NEUROHYPOPHYSIAL HORMONAL CONTROL OF KIDNEY FUNCTION IN THE EUROPEAN EEL (ANGUILLA ANGUILLA L.) ADAPTED TO SEA-WATER OR FRESH WATER

Abstract

Low doses of arginine-vasotocin (AVT), isotocin and oxytocin (1 pg–1 ng/kg body weight) were antidiuretic in eels adapted to fresh water but not in those adapted to sea-water. High doses (more than 10 ng/kg) were always diuretic. No effects on tubular water reabsorption were observed and the glomerular filtration rate (GFR) was proportional to the maximum reabsorptive rate for glucose (T_{m (glucose)}) in eels adapted to sea-water. Increases in urinary flow appeared therefore to result from glomerular recruitment. Infusion of AVT or isotocin at low rates reduced the GFR and urinary flow of freshwater eels to the levels found in seawater eels. Vasopressin (lysine or arginine) had no direct effect on kidney function in freshwater eels but blocked both the diuretic and antidiuretic actions of the other hormones. When infused into seawater eels it was diuretic. This effect could have been due to blockade of the actions of endogenous AVT and/or isotocin.