Arginine vasopressin metabolic clearance and production rates in fetal sheep, pregnant ewes, and lambs.

Arginine vasopressin (AVP) metabolic clearance rates (MCR) and production rates (PR) were measured in chronically catheterized fetuses, maternal ewes (130-135 days of gestation), and 1- to 6-month-old sheep using constant infusion noncompartmental kinetic methodology. No significant differences in mean basal plasma AVP levels, MCR rates or PR were found among the fetuses, maternal ewes or lambs. MCR of AVP did not change with steady-state plasma AVP levels varying from 2 to 68 micronmicron/ml. Neither the placenta nor the fetal kidney appear to play a significant role in AVP metabolic clearance.