PROLACTIN AND OSMOREGULATION IN TELEOST FISHES - A REVIEW

This review covers a new field, in which only a few species have been investigated, and any generalizations must be very tentative. Prolactin is able to promote survival in freshwater of certain hypophysectomized teleosts, mostly cyprinodonts, which require the pituitary gland for freshwater tolerance. In Fundulus heteroclitus, Anguilla anguilla, and Poecilia latipinna prolactin has been shown to ameliorate the fall in blood electrolyte level that follows hypophysectomy in freshwater, and in the first two species it acts to limit the sokium outflux from the body in freshwater, mainly at the gills, although in other fishes (Gasterosteus, Fundulus kansae) a renal effect has been demonstrated. Prolactin is probably one of several hormones that regulate electrolyte metabolism in freshwater. It has not been found to exert an effect on electrolyte regulation in seawater. Evidence is reviewed that indicates the physiological involvement of endogenous fish prolactin in Poecilia latipinna in freshwater. © 1969.