Glomerular filtration changes during vasotocin-induced antidiuresis in kelp gulls

In conscious kelp gulls, intravenous infusion of arginine vasotocin (AVT) at rates of 0.03, 0.1, 0.3, and 1.0 ng.kg-1.min-1 resulted in a linear relationship between the log values of the AVT plasma concentrations (measured by radioimmunoassay) and the infusion rates, which indicated a plasma clearance rate for AVT of 15.4 ml.min-1.kg-1 when endogenous AVT formation is considered. Evaluation of the renal actions of AVT at each dose level showed that antidiuresis was consistently associated with reductions in glomerular filtration rate as well as changes in tubule water permeability. Thus the water-conserving action of plasma AVT on the kelp gull kidney involves contributions from both glomerular and tubular mechanisms over the entire physiological range found in these birds.