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1 Department of Bioscience, University of Strathclyde, Glasgow G1 1XW, UK
2 Inserm U809, Faculté de Médecine René Descartes- site Necker, Université Paris Descartes, F-75015 Paris, France
3 College of Osteopathic Medicine, Edison Biotechnology Institute, Ohio University, Athens, Ohio 45701, USA
(Requests for offprints should be addressed to D J Flint; Email: david.flint{at}strath.ac.uk)
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The PRL receptor (PRLR) belongs to the cytokine receptor superfamily and although it is widely distributed in various tissues, with the exception of birds (Bole-Feysot et al. 1998, Ohkubo et al. 1998), the receptor had not been detected in white adipose tissue. However, Ling et al.(2000) using reverse transcriptase-PCR, identified three PRLR isoforms in mouse adipose tissue, and also detected the protein by immunoblotting and showed it to be upregulated in lactation. They proceeded to show that PRL could induce suppressor of cytokine signaling proteins in adipocytes cultured in vitro, or in adipose tissue of PRL-transgenic mice, providing evidence for induction of intracellular signaling in the adipocyte itself, rather than in other cell types present in adipose tissue (Ling & Billig 2001). Furthermore, insulin-induced leptin secretion was inhibited by PRL, suggesting that PRL was acting, like GH, as an insulin-antagonist. PRL receptors have also been reported to be present in human adipose tissue (Ling et al. 2003) and PRL was shown to inhibit both basal- and cortisol-induced lipoprotein lipase activity, once again mimicking the effects of GH. This series of studies provide compelling evidence for re-examination of the effects of PRL on adipose tissue in vivo.
GH has clear-cut effects on growth and nutrient partitioning between muscle and adipose tissue. Following hypophysectomy in rats, body fat increases, lean body mass decreases and such changes can be normalized by GH (Scow 1959). Similarly, transgenic expression of an inactive GH or disruption of the GH receptor (GHR) in mice results in an obese phenotype (Oberbauer et al. 1997, Berryman et al. 2004). There are clearly direct effects of GH on preadipocyte and adipocyte function, mediated via the GHR (Fagin et al. 1980, Vikman et al. 1991), although some of its actions have been proposed to be indirect, mediated via insulin-like growth factor-I (IGF-I). This led to the proposal of the dual effector hypothesis by Green et al.(1985) which proposed that GH primes mesenchymal cells so that IGF-I can selectively promote cell multiplication, resulting in the clonal expansion of newly differentiated cells. Despite these numerous reports, the effects of GH on adipose tissue proliferation and differentiation remain an area of considerable debate. For example, GH has been demonstrated to exhibit contrasting effects on preadipocyte cell lines when compared with primary preadipocytes. Thus, in clonal cell lines like 3T3-F442A, GH has been demonstrated to decrease proliferation and increase differentiation of preadipocytes (Morikawa et al. 1982, Green et al. 1985). In contrast, GH stimulates the proliferation of preadipocytes in primary cultures from rat and human adipose tissue and consequently inhibits the adipocyte differentiation process in these cells (Wabitsch et al. 1996a,b). The ability of GH to stimulate the differentiation of clonal preadipocyte cell lines is consistent with the ability of GH to regulate cellular differentiation in a variety of tissues, including osteoblasts (Kassem et al. 1993), osteoclasts (Nishiyama et al. 1996), and myoblasts (Ewton & Florini 1980). In 3T3-F442A cells, the initial effect of GH is to block cell division and involves decreased expression of cyclin D1 (Corin et al. 1990, Tang et al. 1995, Wiepz et al. 1997, Kim et al. 1999). The mechanism by which GH inhibits the differentiation of primary preadipocytes into adipocytes has, however, not been studied as extensively as the differentiation program that occurs in cell lines, and thus, which of these in vitro responses most closely represents the situation in vivo, is unclear.
In light of these conflicting data, we examined adipocyte development in two mouse models of PRL- and GH-deficiency, the PRLR gene disrupted or knockout (ko) mouse (Ormandy et al. 1997) and the GH receptor gene disrupted or ko mouse (Zhou et al. 1997). In our initial study of the PRLRko mouse, adipose tissue accretion was reduced, particularly in females and this became progressively more evident with age (Freemark et al. 2001). In addition, in female PRLRko mice, there was a significant reduction in serum leptin concentrations. The present study aimed to determine the role of changes in cell number and size in the alterations in adipose tissue mass in vivo and to examine the proliferation, differentiation, and hormonal responses of preadipocytes in vitro in both PRLRko and GHRko mice.
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Materials and Methods |
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The production of both GHRko and PRLRko mice has previously been described (Ormandy et al. 1997, Zhou et al. 1997). All experimental designs and procedures were in agreement with the guidelines of the Animal Ethics Committee of the French Ministère de l’Agriculture. The GHR–/–, PRLR–/– mice, and their wild-type siblings (+/+), were in the inbred 129/Sv background. Female mice were housed on a 12 h light:12 h darkness cycle at 22 °C with food and water available ad libitum. Food intakes were monitored at weekly intervals throughout the experiment for PRLRko mice and during the period 2–4 months in GHRko mice. PRLRko mice were killed by cervical dislocation at either 5 or 12 months of age. GHRko mice were killed at 3–4 or 12 months of age.
Preparation of adipocytes and preadipocytes
Adipose tissues from the s.c. (abdominal inguinal) and parametrial depots were dissected, weighed, and a portion chopped with scissors and digested with collagenase. Isolated adipocytes were prepared as previously described, with the exception that the cells were not washed by flotation, in order to avoid the loss of very small adipocytes, which otherwise leads to bias in the estimation of mean cell volume (Doris et al. 1994). Adipocyte volumes were determined by capturing images of the isolated adipocytes and determining cell diameters using a Nikon E800 microscope equipped with a video camera and Lucia archive software.
Proliferation studies
A separate portion of tissue was used to prepare precursor adipocytes by centrifugation of the collagenase digest at 100 g for 5 min. The pellet, containing the precursors, was washed three times and the cells resuspended and counted in a hemocytometer. For proliferation studies, 5000 cells were added to 96-well plates in 100 µl Dulbecco’s modified Eagle’s medium (DMEM) containing 10% fetal calf serum (FCS). Cellular proliferation was determined on a daily basis by adding 10 µl water-soluble tetrazolium salt (WST)-1 into triplicate wells and incubating at 37 °C for 1–2 h. Absorbances were read at 450 nm. A standard curve was used to determine the relationship between absorbance after incubation with WST-1 and known cell numbers, added to culture wells.
Differentiation
For differentiation studies, 50 000 cells were added to six wells of a 24-well plate and cultured in DMEM containing 10% FCS until 2–3 days post-confluence. At this point, three wells were induced to differentiate with a mixture of insulin (1 µg/ml), dexamethasone (100 ng/ml), tri-iodothyronine (T3) (10 ng/ml), and 3-isobutyl-1-methylxanthine (IBMX) (100 µg/ml) in serum-free DMEM, whilst three wells served as controls for spontaneous differentiation in the presence of DMEM without additions. Medium was replaced every 3–4 days and after 10 days, cells were washed, fixed in 4% paraformaldehyde and stained with oil red O, which is lipid soluble and allows quantification of lipid accumulation in the cells. After 2 h, excess stain was removed with three washes in distilled H2O and the cells were then photographed before being incubated in 60% isopropanol to solubilize the dye in order to determine the absorbance at 490 nm.
Insulin and isoproterenol sensitivity
Cells that had been cultured and induced to differentiate for 7 days in 96-well plates, as previously described, were washed three times and then cultured for 24 h in various concentrations of either insulin or isoproterenol in serum-free DMEM. The response to insulin was determined by measuring glucose uptake from the medium over 24 h using O-dianisidine, whilst isoproterenol sensitivity was determined by measuring glycerol release into the medium, as a measure of lipolysis, as previously described (Doris et al. 1994).
Statistical analyses
Comparisons were made either using Student’s paired or unpaired t-test or, where multiple comparisons were made by ANOVA, followed by post hoc tests involving the Bonferroni correction.
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Results |
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PRLRko mice showed no significant difference in body weight at either 5 or 12 months of age and with no significant changes in food intake (results not shown). In contrast, GHRko mice were significantly lighter than their wild-type (wt) counterparts (wt 39.1 ± 1.7 g; ko 19.3 ± 1.8 g, mean ± S.E.M. P<0.01, Student’s t-test). They also ate approximately 75% of the quantity of wt animals (results not shown). Despite the fact that PRLRko mice had similar body weights to controls, adipose tissue mass was reduced. The weight of both the parametrial and s.c. depots were decreased by 45–50% inyoung animals (Fig. 1a
). These changes were almost completely explained by similar decreases in the number of adipocytes at each site (Fig. 1b), with no significant changes in mean adipocyte volume (Fig. 1c). In older animals, the decrease in parametrial adipose tissue weight was still evident (Fig. 1d ) and again explained by a decrease in cell numbers (Fig. 1e). In contrast, the effect upon s.c. adipose tissue was almost completely lost in older animals (Fig. 1d ), although this was as a result of a compensatory increase in adipocyte volume (Fig. 1f ) in the presence of a significant reduction in adipocyte numbers in s.c. tissue (Fig. 1e).
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). In stark contrast, the effect on s.c. adipose tissue was much less, being decreased by just 35% (Fig. 2a). The decrease in parametrial adipose tissue weight was due to a 75% decrease in both the number and size of adipocytes (Fig. 2b and c). Again, in contrast, whereas the volume of s.c. adipocytes was decreased by about 50%, the number of s.c. adipocytes was almost doubled (Fig. 2b and c). Even when expressed per unit of body weight, the parametrial depot was still significantly reduced in GHRko mice (wt, 7.2 ± 0.6 g/kg body weight, GHRko 3.0 ± 0.7 g/kg, P<0.01), whereas the s.c. depot was significantly increased (wt, 2.2 ± 0.2 g/kg body weight, GHRko, 4.1 ± 0.7 g/kg, P<0.05, Student’s t-test). Although the parametrial depot increased in size in older GHRko mice, it still remained decreased by 75% compared with wt animals (Fig. 2d ) and this was again due to approximately equivalent decreases in the number (Fig. 2e) and size (Fig. 2f ) of adipocytes. The weight of the s.c. depot in wt and GHRko mice was not significantly different at 12 months of age (Fig. 2d ). However, this masked the fact that the s.c. depot contained two to three times as many adipocytes in GHRko mice (Fig. 2e), whilst mean adipocyte volume was decreased by a similar magnitude (Fig. 2f ).
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). Similarly, in GHRko mice, rates of proliferation of preadipocytes derived from the s.c. site were unaffected (Fig. 3b). However, this was not the case for cells derived from the parametrial site of GHRko mice, since these failed to proliferate during the 7-day culture period in all six animals tested (Fig. 3b).
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). However, the individual response of cells varied markedly in stimulated cells, with lipid accumulation initially involving many small lipid droplets. Ultimately, these droplets coalesced to form smaller numbers of larger lipid droplets becoming highly characteristic of the fully differentiated adipocyte. The degree of differentiation was quantified by solubilization of the oil red O staining (Fig. 5). In wt animals, the magnitude of lipid accumulation was considerably greater in the s.c. depot compared with the parametrial (note the difference in axis scales) and was also considerably greater in young animals compared with older animals (this was particularly evident in the s.c. depot). Differentiation potential was unaffected in PRLRko animals, when compared with wt animals, independently of adipose tissue site or age, under either basal- or hormone-stimulated conditions (Fig. 5).
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). Differentiation in s.c. adipose tissue of GHRko mice was identical to that of wt animals (Fig. 6, lower panel). Once again, however, preadipocytes from the parametrial depot of GHRko mice behaved anomalously in vitro, showing no differentiation response (Fig. 6, upper panel).
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). Insulin sensitivity in GHRko mice was also similar to wt mice in adipocytes derived from the s.c. depot, but parametrial adipocytes of GHRko mice were completely unresponsive to insulin (Fig. 7b).
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). Sensitivity to isoproterenol in GHRko mice was also similar to wt mice in the s.c. depot but, as in the case for insulin, parametrial adipocytes of GHRko mice were completely unresponsive to this lipolytic agent (Fig. 8b).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The effect of PRLR deficiency on adipocyte numbers was unexpected, since one possible explanation for such a decrease in adipose tissue mass would be a decrease in food intake. However, we noted no change in food intake in our animals. Furthermore, the effect of food restriction is to decrease adipocyte volume, not number. In addition, we noted that the effects of PRLR-deficiency on adipocyte numbers persisted until 1 year of age, although the effect on adipose tissue mass was partially abrogated by an increase in adipocyte volume in the s.c. but not the parametrial site. This is the first report of site-specific regulation of adipose tissue metabolism by PRL.
In GHRko mice, the situation was distinctly different, not least, perhaps, because absence of the GHR leads to severe dwarfism. The development of the parametrial adipose tissue depot was dramatically impaired and this impairment was also due to a decrease in the number of adipocytes, although there was, in addition, a significant reduction in adipocyte volume. Such a finding provides strong support for a stimulatory effect of GH on both adipocyte proliferation (cell numbers) and differentiation (adipocyte lipid content or mean cell volume). In complete contrast, however, adipose tissue development in s.c. depots of GHRko mice was not significantly impaired even though these mice weighed only 40–50% of the weight of wt mice. In fact, adipocyte numbers were doubled in s.c. adipose tissue of GHR-deficient animals, whereas mean adipocyte volume was significantly decreased. The fact that, in vitro, cells from the s.c. depot also proliferated, differentiated, and responded to hormones in identical fashion to those of wt animals, suggests that the effects of GH on development and function of the s.c. depot were not due to intrinsic changes but, as for PRLRko mice, reflected events pertaining in vivo. In contrast to the s.c. site, both proliferation and differentiation in vivo of adipocytes from the parametrial depot were critically dependent upon the presence of the GHR. The distinction between the apparent fundamental requirement for GH in the parametrial depot and the total independence of the s.c. depot is clearly worthy of further investigation. In addition to identifying these site-specific effects, we also demonstrated, for the first time, that absence of the GHR creates intrinsic changes in adipocytes from this depot, which persist for at least 10 days in vitro. These findings confirm and extend a previous study where we examined the effects of an antiserum to GH which, when administered to neonatal rats, also produced major decreases in parametrial but not s.c. fat (Flint & Gardner 1993). Whilst the effects upon the parametrial depot described in our study clearly demonstrate that GH is required for adipocyte proliferation and differentiation in vivo, in similar fashion to that seen in 3T3-F442A cells in vitro, the site-specific effects of GH may in part explain the contradictory results obtained with different cell lines, or in comparisons of primary cell culture, where cells have originated from different anatomical sites.
How might these site-specific differences be explained? There is differential expression of the GHR depending on the location of the adipose tissue depot with, for example, high level expression of the GHR in the epididymal fat pad compared with the retroperitoneal fat pad in male rats (LaFranchi et al. 1985). However, no such studies have compared GHR numbers in s.c. and parametrial depots of female mice. Expression of the receptor is regulated during the differentiation process with increased levels of receptor expression during adipocyte differentiation (Landron et al. 1987, Zou et al. 1997) and these different levels of receptor expression could explain the differential sensitivity to GH of individual adipose sites. However, the differences in GHR expression reported have generally not been large and the differences in adipose tissue development in the respective sites have, similarly, not been dramatically different. We thus believe that the dramatic changes in development of the parametrial depot in GHRko mice described in this study make this site an excellent model to examine the nature of this effect of GH.
In our study, the depot most protected from GH-deficiency, the s.c., possesses a large lymph node in the inguinal region, whereas the parametrial depot does not. Pond (1999) has proposed an intriguing hypothesis, which relates to one of the latest proposed therapeutic uses of GH. This involves the lipodystrophic condition in HIV patients where adipose tissue accumulates specifically in the abdominal cavity. Pond noted that, even in the face of starvation, some depots which are rich in lymphoid tissue are conserved. She suggests that this is a process whereby lymphoid tissues are provided with a local energy source so that immune responses are not compromised (Pond & Mattacks 2002, Mattacks et al. 2003, Pond 2003). Thus, part of the GH insensitivity of the s.c. depot may be due to the influence of lymphoid cytokines.
In summary, our studies provide a number of novel observations. We demonstrate that, although the parametrial depot becomes the major depot as female mice age, the s.c. depot differentiates to a much greater extent in vitro. We also noted a considerable decrease in the ability of preadipocytes from both sites to accumulate lipid in vitro as the animals aged. For the first time, we describe effects of PRL on adipocyte development. These are not explicable in terms of effects on appetite, since the reduction in mass was attained by decreased numbers of adipocytes, rather than a decrease in their size. We also demonstrate that the actions of GH are site specific, a finding which may explain the conflicting results from in vitro studies involving both primary tissue culture and preadipocyte cell lines, which may be due to derivation of precursor cells from different anatomical sites in vivo. Finally, we describe intrinsic defects in parametrial adipocytes from GHRko mice and believe that this provides an excellent model to identify novel factors involved in this long-lived effect of GH.
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Acknowledgements |
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References |
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Berryman DE, List EO, Coschigano KT, Behar K, Kim JK & Kopchick JJ 2004 Comparing adiposity profiles in three mouse models with altered GH signaling. Growth Hormone and IGF Research 14 309–318.
Bole-Feysot C, Goffin V, Edery M, Binart N & Kelly PA 1998 Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice. Endocrine Reviews 19 225–268.
Corin RE, Guller S, Wu KY & Sonenberg M 1990 Growth hormone and adipose differentiation: growth hormone-induced antimitogenic state in 3T3-F442A preadipose cells. PNAS 87 7507–7511.
Doris R, Vernon RG, Houslay MD & Kilgour E 1994 Growth hormone decreases the response to anti-lipolytic agonists and decreases the levels of Gi2 in rat adipocytes. Biochemical Journal 297 41–45.
Ewton DZ & Florini JR 1980 Relative effects of the somatomedins, multiplication-stimulating activity, and growth hormone on myoblasts and myotubes in culture. Endocrinology 106 577–583.
Fagin KD, Lackey SL, Reagan CR & DiGirolamo M 1980 Specific binding of growth hormone by rat adipocytes. Endocrinology 107 608–615.
Fielder PJ & Talamantes F 1987 The lipolytic effects of mouse placental lactogen II, mouse prolactin, and mouse growth hormone on adipose tissue from virgin and pregnant mice. Endocrinology 121 493–497.
Flint DJ & Gardner MJ 1993 Influence of growth hormone deficiency on growth and body composition in rats: site-specific effects upon adipose tissue development. Journal of Endocrinology 137 203–211.
Freemark M, Fleenor D, Driscoll P, Binart N & Kelly P 2001 Body weight and fat deposition in prolactin receptor-deficient mice. Endocrinology 142 532–537.
Genazzani AR, Benuzzi-Badoni M & Felber JP 1969 Human chorionic somato-mammotropine (HCSM): lipolytic action of a pure preparation on isolated fat cells. Metabolism 18 593–598.[CrossRef][Web of Science][Medline]
Green H, Morikawa M & Nixon T 1985 A dual effector theory of growth-hormone action. Differentiation 29 195–198.[CrossRef][Web of Science][Medline]
Houseknecht KL, Bauman DE, Vernon RG, Byatt JC & Collier RJ 1996 Insulin-like growth factors-I and -II, somatotropin, prolactin, and placental lactogen are not acute effectors of lipolysis in ruminants. Domestic Animal Endocrinology 13 239–249.[CrossRef][Web of Science][Medline]
Iliou JP & Demarne Y 1987 Evolution of the sensitivity of isolated adipocytes of ewes to the lipolytic effects of different stimuli during pregnancy and lactation. International Journal of Biochemistry 19 253–258.
Kassem M, Blum W, Ristelli J, Mosekilde L & Eriksen EF 1993 Growth hormone stimulates proliferation and differentiation of normal human osteoblast-like cells in vitro. Calcified Tissue International 52 222–226.[CrossRef][Web of Science][Medline]
Kim SO, Houtman JC, Jiang J, Ruppert JM, Bertics PJ & Frank SJ 1999 Growth hormone-induced alteration in ErbB-2 phosphorylation status in 3T3-F442A fibroblasts. Journal of Biological Chemistry 274 36015–36024.
LaFranchi S, Hanna CE, Torresani T, Schoenle E & Illig R 1985 Comparison of growth hormone binding and metabolic response in rat adipocytes of epididymal, subcutaneous, and retroperitoneal origin. Acta Endocrinologica 110 50–55.
Landron D, Dugail I, Ardouin B, Quignard-Boulange A & Postel-Vinay MC 1987 Growth hormone binding to cultured preadipocytes from obese fa/fa rats increases during cell differentiation. Hormone and Metabolic Research 19 403–406.[Web of Science][Medline]
Ling C & Billig H 2001 PRL receptor-mediated effects in female mouse adipocytes: PRL induces suppressors of cytokine signaling expression and suppresses insulin-induced leptin production in adipocytes in vitro. Endocrinology 142 4880–4890.
Ling C, Hellgren G, Gebre-Medhin M, Dillner K, Wennbo H, Carlsson B & Billig H 2000 Prolactin (PRL) receptor gene expression in mouse adipose tissue: increases during lactation and in PRL-transgenic mice. Endocrinology 141 3564–3572.
Ling C, Svensson L, Oden B, Weijdegard B, Eden B, Eden S & Billig H 2003 Identification of functional prolactin (PRL) receptor gene expression: PRL inhibits lipoprotein lipase activity in human white adipose tissue. Journal of Clinical Endocrinology and Metabolism 88 1804–1808.
Mattacks CA, Sadler D & Pond CM 2003 The cellular structure and lipid/protein composition of adipose tissue surrounding chronically stimulated lymph nodes in rats. Journal of Anatomy 202 551–561.[CrossRef][Web of Science][Medline]
Morikawa M, Nixon T & Green H 1982 Growth hormone and the adipose conversion of 3T3 cells. Cell 29 783–789.[CrossRef][Web of Science][Medline]
Nishiyama K, Sugimoto T, Kaji H, Kanatani M, Kobayashi T & Chihara K 1996 Stimulatory effect of growth hormone on bone resorption and osteoclast differentiation. Endocrinology 137 35–41.[Abstract]
Oberbauer AM, Stern JS, Johnson PR, Horwitz BA, German JB, Phinney SD, Beermann DH, Pomp D & Murray JD 1997 Body composition of inactivated growth hormone (oMt1a-oGH) transgenic mice: generation of an obese phenotype. Growth, Development and Aging 61 169–179.[Web of Science][Medline]
Ohkubo T, Tanaka M, Nakashima K, Talbot RT & Sharp PJ 1998 Prolactin receptor gene expression in the brain and peripheral tissues in broody and nonbroody breeds of domestic hen. General and Comparative Endocrinology 109 60–68.[CrossRef][Web of Science][Medline]
Oller do Nascimento CM, Ilic V & Williamson DH 1989 Re-examination of the putative roles of insulin and prolactin in the regulation of lipid deposition and lipogenesis in vivo in mammary gland and white and brown adipose tissue of lactating rats and litter-removed rats. Biochemical Journal 258 273–278.[Web of Science][Medline]
Ormandy CJ, Camus A, Barra J, Damotte D, Lucas B, Buteau H, Edery M, Brousse N, Babinet C, Binart N et al. 1997 Null mutation of the prolactin receptor gene produces multiple reproductive defects in the mouse. Genes and Development 11 167–178.
Pond CM 1999 Physiological specialisation of adipose tissue. Progress in Lipid Research 38 225–248.[CrossRef][Web of Science][Medline]
Pond CM 2003 Paracrine interactions of mammalian adipose tissue. Journal of Experimental Zoology. Part A, Comparative Experimental Biology 295 99–110.
Pond CM & Mattacks CA 2002 The activation of the adipose tissue associated with lymph nodes during the early stages of an immune response. Cytokine 17 131–139.[CrossRef][Web of Science][Medline]
Scow RO 1959 Effect of growth hormone and thyroxine on growth and chemical composition of muscle, bone and other tissues in thyroidectomized-hypophysectomized rats. American Journal of Physiology 196 859–865.
Stewart WC, Baugh JE Jr, Floyd ZE & Stephens JM 2004 STAT 5 activators can replace the requirement of FBS in the adipogenesis of 3T3-L1 cells. Biochemical and Biophysical Research Communications 324 355–359.[CrossRef][Web of Science][Medline]
Strange RC & Swyer GI 1974 The effect of human placental lactogen on adipose tissue lipolysis. Journal of Endocrinology 61 147–152.
Tang B, Jeoung DI & Sonenberg M 1995 Effect of human growth hormone and insulin on [3H]thymidine incorporation, cell cycle progression, and cyclin D expression in 3T3-F442A preadipose cells. Endocrinology 136 3062–3069.[Abstract]
Turtle JR & Kipnis DM 1967 The lipolytic action of human placental lactogen on isolated fat cells. Biochimica et Biophysica Acta 144 583–593.[Medline]
Vikman K, Carlsson B, Billig H & Eden S 1991 Expression and regulation of growth hormone (GH) receptor messenger ribonucleic acid (mRNA) in rat adipose tissue, adipocytes, and adipocyte precursor cells: GH regulation of GH receptor mRNA. Endocrinology 129 1155–1161.
Wabitsch M, Heinze E, Hauner H, Shymko RM, Teller WM, De Meyts P & Ilondo MM 1996a Biological effects of human growth hormone in rat adipocyte precursor cells and newly differentiated adipocytes in primary culture. Metabolism 45 34–42.[CrossRef][Web of Science][Medline]
Wabitsch M, Braun S, Hauner H, Heinze E, Ilondo MM, Shymko R, De Meyts P & Teller WM 1996b Mitogenic and antiadipogenic properties of human growth hormone in differentiating human adipocyte precursor cells in primary culture. Pediatric Research 40 450–456.[Web of Science][Medline]
Wiepz GJ, Houtman JC, Cha D & Bertics PJ 1997 Growth hormone attenuation of epidermal growth factor-induced mitogenesis. Journal of Cellular Physiology 173 44–53.[CrossRef][Web of Science][Medline]
Zhou Y, Xu BC, Maheshwari HG, He L, Reed M, Lozykowski M, Okada S, Cataldo L, Coschigamo K, Wagner TE et al. 1997 A mammalian model for Laron syndrome produced by targeted disruption of the mouse growth hormone receptor/binding protein gene (the Laron mouse). PNAS 94 13215–13220.
Zou L, Menon RK & Sperling MA 1997 Induction of mRNAs for the growth hormone receptor gene during mouse 3T3-L1 preadipocyte differentiation. Metabolism 46 114–118.[CrossRef][Web of Science][Medline]
Received 28 April 2006
Accepted 6 July 2006
Made available online as an Accepted Preprint 4 August 2006
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P<0.01 compared with wild-type animals. Note the difference in axis scales between young and old animals.
P<0.001 compared with wild-type animals. Note the difference in axis scales between young and old animals.
), ko parametrial (
), wt s.c. (
), and ko s.c. (•) cell numbers were determined, in triplicate, on a daily basis by addition of 10 µl water-soluble tetrazolium salt (WST)-1 followed by incubation for 1–2 h. Cell numbers were calculated from a standard curve in which WST-1 values were calculated from serial dilutions of a known number of cells added to tissue culture wells under identical conditions. Values are means ± S.E.M. of four to six animals.
