HOME HELP CONTACT US SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Matthaei, S Articles by Klein, H H Search for Related Content PubMed PubMed Citation Articles by Matthaei, S Articles by Klein, H H

To examine the effect of thyroid hormone status on insulin action in isolated rat adipocytes, age- and weight-matched Sprague–Dawley rats were rendered hypothyroid (h) by i.p. injection of 2 mCi [¹³¹I]/kg. Another group of rats was made hyperthyroid (H) by i.p. injection of 500 µg l-thyroxine/kg/day for 7 days. The T₄ levels in experimental groups were: controls, 33·5±0·95; h, 12·3±1·59: H, 133·2±8·8 µg/l. Adipocytes were isolated and 3-O-methylglucose transport (GT), insulin binding (IB) and insulin receptor kinase activity (IRKA) were determined. Subcellular membrane fractions (low-density microsomes, plasma membranes) were prepared and GLUT1 and GLUT4 glucose transporter immunodetected.

Hyperthyroidism caused no significant effect on either IB or IRKA but increased insulin-stimulated GT by 43·6%. This increase of GT was associated with an increase of primarily GLUT4 glucose transporters. Hypothyroidism was associated with both increased insulin receptor affinity and enhanced IRKA. Despite a marked reduction of primarily GLUT4 glucose transporters, basal and insulinstimulated GT was not reduced when compared with control.

These results suggest that (1) in hyperthyroidism, increased insulin-stimulated glucose transport is associated with an increase of primarily GLUT4 glucose transporters, which may be responsible for the increment of peripheral glucose utilization in hyperthyroidism, and (2) the effect of hypothyroidism on insulin action in adipocytes is characterized by a state of increased insulin sensitivity, as indicated by the increase in insulin receptor affinity and tyrosine kinase activity. Despite the marked reduction of primarily GLUT4 glucose transporters, insulin-stimulated glucose transport is not diminished, which may suggest that functional activity of plasma membrane glucose transporters is enhanced in hypothyroidism.

Journal of Endocrinology (1995) 144, 347–357

This article has been cited by other articles:

				F. Grunwald and H.-J. Biersack FDG PET in Thyroid Cancer: Thyroxine or Not? J. Nucl. Med., December 1, 2000; 41(12): 1996 - 1998. [Full Text] [PDF]

				C. M. Ferrara, T. H. Reynolds, M. J. Zarnowski, J. T. Brozinick Jr., and S. W. Cushman Short-term exercise enhances insulin-stimulated GLUT-4 translocation and glucose transport in adipose cells J Appl Physiol, December 1, 1998; 85(6): 2106 - 2111. [Abstract] [Full Text] [PDF]