Overwinter fasting and re-feeding in rainbow trout: plasma growth hormone and cortisol levels in relation to energy mobilization

Pottinger, T. G.; Rand-Weaver, M.; Sumpter, J.P.. 2003 Overwinter fasting and re-feeding in rainbow trout: plasma growth hormone and cortisol levels in relation to energy mobilization. Comparative Biochemistry and Physiology Part B, 136 (3). 403-417. 10.1016/S1096-4959Ž03.00212-4

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Abstract/Summary

This study investigated the roles of cortisol and growth hormone during a period of fasting in overwintering salmonid fish. Indices of carbohydrate (plasma glucose, liver glycogen), lipid (plasma free fatty acids) and protein metabolism (plasma protein, total plasma amino acids) were determined, together with plasma growth hormone (GH), cortisol and somatolactin levels (SL) at intervals in three groups of rainbow trout (continuously fed; fasted for 9 weeks then fed; fasted for 17 weeks). In fasted fish, a decline in body weight and condition factor was accompanied by reduced plasma glucose and hepatic glycogen and increased plasma FFA. No consistent elevation of plasma GH occurred until after 8 weeks of fasting when plasma GH levels increased nine-fold. No changes were observed in plasma total protein and AA until between weeks 13 and 17 when both were reduced significantly. When previously fasted fish resumed feeding, plasma glucose and FFA, and hepatic glycogen levels rapidly returned to control values and weight gain resumed. No significant changes in plasma cortisol levels, related to feeding regime, were evident at any point during the study and there was no evidence that SL played an active role in the response to fasting. The results suggest that overwinter fasting may not represent a significant nutritional stressor to rainbow trout and that energy mobilisation during fasting may be achieved without the involvement of GH, cortisol or SL.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/S1096-4959Ž03.00212-4
Programmes:	CEH Programmes pre-2009 publications > Water
UKCEH and CEH Sections/Science Areas:	_ Environmental Chemistry & Pollution
ISSN:	1096-4959
Additional Information. Not used in RCUK Gateway to Research.:	NOTICE: The attached pdf is the author’s version of a work that was accepted for publication in Comparative Biochemistry and Physiology Part B. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Comparative Biochemistry and Physiology Part B, 136(3). 403-417. 10.1016/S1096-4959Ž03.00212-4 www.elsevier.com/
Additional Keywords:	cortisol, fasting, free fatty acids, growth hormone, glucose, glycogen, Oncorhynchus mykiss, somatolactin
NORA Subject Terms:	Ecology and Environment Zoology Biology and Microbiology
Date made live:	23 Jun 2015 09:01 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/510679

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