Water and sodium homeostasis in conscious rabbits: role of arginine-vasopressin.
The aim of this study was to assess the role of arginine-vasopressin (AVP) on extracellular water distribution (VE) and on the urinary excretion of sodium in conscious rabbits with or without water deprivation. The study included two groups of animals. The first group involved two subgroups, both receiving an infusion of 0.9% NaCl-5% glucose (50-50, v:v) at the rate of 24 ml/hr to adequately hydrate the rabbits, but one received 2.5 ng/min/kg of AVP with the infusion; 120 min later, a bolus of inulin was injected to assess the distribution in the extracellular water. The rabbits of the second group were divided into 3 subgroups, receiving a 0.9% NaCl-5% glucose (50-50, v:v) infusion, at the rate of 6 ml/min; two subgroups received AVP, at the rate of 2.5 or 5 ng/min/kg; 40 minutes later, all animals received a bolus of inulin. In adequately hydrated rabbits, the infusion of AVP generated plasma levels of 35 +/- 7 pg/ml; the VE decreased from 204 +/- 23 to 111 +/- 10 ml/kg (p < 0.01) because of a decrease in plasma (VP) and interstitial volumes (VI). In the same group, natriuresis and osmolal clearance increased and free water clearance decreased. In rabbits deficiently hydrated, AVP reached plasma levels of 47 +/- 18 and 86 +/- 12 pg/ml following the 2.5 and 5 ng/min/kg infusions, respectively. In these animals, high plasma levels of AVP did not diminish VE but decreased the diuresis and osmolal clearance. It is concluded that in adequately hydrated rabbits, pathophysiological plasma levels of AVP shift the water from the VE to the intracellular space and increase the natriuresis, but in partially hydrated rabbits, the infusion of AVP maintains plasma volume constant because of an antidiuretic effect.
Babini
R
R
Department of Pharmacology, Faculty of Medicine, University of Montréal, Québec, Canada.
du Souich
P
P
D000818:Animals; D001127:Arginine Vasopressin / Q000493:pharmacokinetics* / Q000494:pharmacology; D003681:Dehydration / Q000378:metabolism*; D005919:Glomerular Filtration Rate; D007262:Infusions, Intravenous; D008297:Male; D009994:Osmolar Concentration; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000187:drug effects
D001127:Arginine Vasopressin; D012964:Sodium