Renal responses to vasoactive hormones in the aglomerular toadfish, Opsanus tau.

Abstract

Abstract Angiotensin and neurohypophysial hormones have been shown to affect renal and cardiovascular function in glomerular fish. In order to determine if these hormones have any tubular actions, we administered angiotensin, arginine vasotocin (AVT), and isotocin intraarterially into the unanesthetized, chronically cannulated, aglomerular toadfish. Angiotensin (100 ng kg −1 min −1 ) increased dorsal aortic pressure, but did not increase urine flow or the urinary excretion rate of Na, K, Cl, or Mg. AVT (50 ng kg −1 min −1 ) increased dorsal aortic blood pressure comparable to the increase after angiotensin. Urine flow and urinary electrolyte excretion increased also in response to AVT, but the effect was highly variable. A bolus injection of isotocin (1000 ng kg −1 ) did not elicit a pressor response, but significantly increased urine flow, urinary Mg concentration, and the urinary excretion of Mg and Cl. These data suggest that isotocin, and perhaps AVT, may act on teleost renal tubules. AVT caused more variable renal effects than isotocin, presumably due to its cardiovascular actions.