Physiology of Trout Natriuretic Peptides

Indiana University, Bloomington IN

Investigators

Abstract

This study will examine the physiology of natriuretic peptides (NPs) in fish. NPs are a family of peptide hormones that decrease blood volume and lower blood pressure in virtually all vertebrates. NPs were first identified in mammals in 1981and although their genetic code was determined a few months later, their physiological function remains unknown to the present time. This proposal questions the applicability of mammalian models in NP research because mammals continually lose water through evaporation and renal excretion and thus are never naturally volume or pressure over-loaded. However, freshwater fish (trout) are chronically volume over-loaded and as the earliest vertebrates that contain all members of the NP family of proteins, they form the basis for the present study. Initially, specific assays will be developed for each trout NP (ANP, CNP, VNP). These assays will be used to determine how NP secretion is affected by independently manipulating water and salt balance via adapting trout to freshwater (volume overload, salt depletion), saltwater (volume depletion, salt overload), and freshwater plus high salt diet (volume and salt overload). Only euryhaline fish, such as trout, thrive in all these conditions and they are the only vertebrates in which these parameters can be controlled independently, non-invasively, and without stress. This information will then be used to examine the effects of physiological doses of NPs on trout fluid balance, in vivo and in vitro cardiovascular and renal function, and identify tissue-specific NP secretory processes. These studies will provide the first comprehensive picture of NP physiology from the vertebrates in which they initially evolved. This project is part of an international collaboration with laboratories in Canada and Japan and it will provide domestic and foreign training for graduate students and domestic training for undergraduates, teachers in secondary education, and high school students.