ARS | Publication request: NOVEL MECHANISMS TO PROMOTE GROWTH IN A COMMERCIALLY-IMPORTANT TELEOST, THE RAINBOW TROUT (ONCORHYNCHUS MYKISS)

Submitted to: Kentucky Academy of Sciences Symposium
Publication Type: Abstract
Publication Acceptance Date: October 7, 2002
Publication Date: November 7, 2002
Citation: Shepherd, B., Drennon, K., Silverstein, J., Vijayan, M., Weber, G.M. 2002. Novel mechanisms to promote growth in a commercially-important teleost, the rainbow trout (oncorhynchus mykiss). Kentucky Academy of Sciences Symposium.

Technical Abstract: The pituitary hormone, growth hormone (GH), and its intermediary, insulin-like growth factor I (IGF-I), have fundamental roles in the regulation of growth in teleosts. Growth hormone secretion is principally controlled by the two neuroendocrine factors, growth hormone-releasing hormone (GHRH) and somatostatin. Recently, a newly discovered hormone, termed "Ghrelin" and growth hormone-releasing peptides (GHRPs: synthetic hexapeptides), which bind to the same receptor (GHRP-receptor) on the pituitary & hypothalamus, have been shown to stimulate GH secretion in vertebrates. The rainbow trout (Oncorhynchus mykiss) is one of the most extensively cultured finfish species in North America and is important to sport fisheries across the United States. In this regard, significant advances, using biotechnology (transgenesis) to increase GH production, have yielded salmon that exhibit a 40-fold increase in growth rate. Despite such advances, it is unlikely that, in the foreseeable future, genetically-modified finfish will obtain approval for human consumption. As a result, other methods must be developed to enhance production of rainbow trout and other commercially-important fish species. Against this background, our efforts are aimed at altering endogenous levels of GH using secretagogues such as GHRPs, or specific combinations of dietary amino acids. To accomplish this, we are working to develop a homologous radio-immunoassay (RIA), using commercially-available products, to measure GH levels in rainbow trout. This new RIA will allow us to determine whether GHRPs, and other GH secretagogues, stimulate plasma GH levels in rainbow trout. We will present results from on-going studies that are aimed at examining the effects of secretagogues (GHRPs, GHRH and Ghrelin) and environmental salinity on GH secretion in rainbow trout.