Glomerular actions of arginine vasotocin in the in situ perfused trout kidney. Amer, Shehla, J. Anne Brown. Department of Biological Sciences, Hatherly Laboratories, University of Exeter, Exeter, EX4 4PS, UK.
APStracts 2:0097R, 1995.
Recent measurements of plasma AVT in teleost fish suggest circulating concentrations of 10-10M-10-12M. Previous studies of the renal actions of AVT in vivo suggest both diuretic and antidiuretic effects, but at unknown circulating concentrations. We have investigated the renal actions of 10-9M and 10-11M AVT in vitro using an in situ perfused kidney preparation of rainbow trout (Oncorhynchus mykiss). AVT increased vascular resistance (23%), reduced perfusate flow (P<0.001) and increased intrarenal aortic pressure (P<0.001). AVT resulted in dose-dependent decreases in urine flow rates, glomerular filtration rates and tubular transport maxima for glucose. AVT at 10-11M reduced relative free water clearances (P<0.01), but U/P inulin ratios were unchanged, while 10-9M AVT reduced U/P inulin ratios (P<0.01) and increased relative free water clearances (P<0.05). The filtering population of glomeruli was reduced by both 10-11M and 10-9M AVT, to approximately one third of the glomeruli, and a similar population of arterially-perfused but non-filtering glomeruli emerged. These results demonstrate that physiological concentrations of AVT have potent glomerular antidiuretic action in the trout, reducing the number of functional glomeruli. 

Received 16 May 1994; accepted in final form 30 March 1995.
APS Manuscript Number R256-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 April 1995.