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This Article Accepted manuscript (PDF) All Versions of this Article: JOE-07-0649v1 199/1/81    most recent 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 Google Scholar Google Scholar Articles by Picha, M. Articles by Borski, R. Search for Related Content PubMed PubMed Citation Articles by Picha, M. Articles by Borski, R.

M Picha, Department of Zoology, North Carolina State University, Raleigh, 27695, United States
M Turano, North Carolina Sea Grant, Raleigh, United States
C Tipsmark, Biology, University of Southern Denmark, Odense, Denmark
R Borski, Department of Zoology, North Carolina State University, Raleigh, United States

Correspondence: Matthew Picha, Email: mepicha{at}unity.ncsu.edu

Abstract

Compensatory growth (CG) is a period of growth acceleration that exceeds normal rates after animals are alleviated of certain growth-stunting conditions. In hybrid striped bass (HSB, Morone chrysops x M. saxatilis), 3 weeks of complete feed restriction results in a catabolic state that, when relieved, renders a subsequent phase of CG. The catabolic state was characterized by depressed levels of hepatic Type I and II GH receptor (Ghr1, Ghr2) and insulin-like growth factor-I (Igf-I) mRNA, along with considerable decreases in plasma IGF-I. The state of catabolism also resulted in significant declines in hepatic Igf-II mRNA and in circulating 40kDa IGF binding protein (IGFBP). Skeletal muscle expression of Ghr2 mRNA was significantly increased. Upon realimentation, specific growth rates (SGR) were significantly higher than sized-matched controls, indicating a period of CG. Hepatic Ghr1, Ghr2, Igf-I and Igf-II mRNA levels along with plasma IGF-I and 40kDa IGFBP increased rapidly during realimentation. Plasma IGF-I and total hepatic Igf-II mRNA were significantly correlated to SGR throughout the study. Skeletal muscle Igf-I mRNA also increased 10-fold during CG. These data suggest that endocrine and paracrine/autocrine components of the GH-IGF axis, namely IGF-I, Igf-II, and Ghr1 and Ghr2, may be involved in CG responses in HSB, with several of the gene expression variables exceeding normal levels during CG. We also demonstrate that normalization of hepatic mRNA as a function of total liver production, rather than as a fraction of total RNA, may be a more biologically appropriate method of quantifying hepatic gene expression when using real-time PCR.