EFFECT OF ARGININE-VASOPRESSIN AND PARATHYROID HORMONE-RELATED PROTEIN ON RENAL-FUNCTION IN THE OVINE FETUS

1. The effects of intravenous infusions of arginine vasopressin (AVP), parathyroid hormone-related protein (PTHrP) and AVP + PTHrP on renal function in intact ovine foetuses at 100-125 days of gestation were examined. 2. A low dose of AVP (5.5 +/- 0.9 pmol/h) increased plasma AVP concentrations from 0.6 pmol/ L to 2.1 +/- 0.4 pmol/ L (mean +/- s.e.m; n = 8). This dose caused a significant reduction in free water clearance (C(H2O); P<0.001), without any significant change in fetal arterial blood pressure, glomerular filtration rate (GFR), or the urinary excretion rates of sodium, calcium or 3', 5'-cyclic adenosine monophosphate (cAMP). 3. Infusions of PTHrP (1 nmol/h), with or without 1 nmol bolus dose, significantly increased (P<0.05) urine osmolality (U(OSM), but did not synergize with AVP in reducing C(H2O). 4. It is concluded that AVP and PTHrP do not act synergistically on the kidney of the intact ovine foetus.