These experiments were designed to evaluate directly the effects of a reduction in renal blood flow on the renal metabolism of vasopressin (ADH) in the anesthetized dog. Renal handling of ADH was measured in three successive 30 min periods, with a 30 min interval between each period. Renal blood flow (RBF) was reduced to 50% at the end of the first period and to 25% at the end of the second period by renal artery constriction (RAC) in 9 of the 18 dogs. The nine unconstricted dogs served as time controls (TC). During the initial 30 min determination, renal clearance of ADH (C(ADH)) averaged 2.8 ± 0.6 and 2.1 ± 0.3 ml/min. kg (means ± SE) in the RAC and TC groups, respectively. Reduction of RBF 50% decreased C(ADH) to 1.2 ± 0.2 ml/min kg; reduction of RBF 75% decreased C(ADH) to 0.6 ± 0.1 ml/min kg. Inulin clearance, which averaged 2.4 ± 0.4 ml/min kg initially, was reduced to 1.3 ± 0.02 ml/min kg during 50% RBF and to zero during 25% RBF (eight dogs). A measurable renal ADH clearance of 0.6 ± 0.1 ml/min kg during 25% RBF, when there was no measurable extraction of inulin, would suggest that some mechanism other than filtration can contribute to the extraction of ADH by the kidney. The urinary ADH clearance was approximately 70% of the renal ADH clearance during the initial clearance period in RAC and TC dogs. This decreased to 34% in the TC dogs during the third clearance period. These changes in urinary excretion of cleared ADH may reflect changes in tubular reabsorption and/or increases in tubular inactivation of ADH.
ASJC Scopus subject areas
- Physiology (medical)