Arginine vasopressin interacts with thromboxane in hydronephrosis

The influence of hydronephrosis (6-10 wk) on the renal vascular response to arginine vasopressin (AVP) was assessed, using isolated perfused normal and hydronephrotic rat kidneys. In normal kidneys, AVP (0.3 nM) reduced renal perfusate flow (RPF) by 55 +/- 7% (P < 0.01). AVP-induced decrements in RPF were reversed partially by diltiazem (10 l-IM) and completely by 10 nM of an AVP (V-1)-receptor antagonist (AVPX). In hydronephrotic kidneys, AVP reduced RPF by 81 +/- 2% (P < 0.01) and constricted afferent (AA) and efferent arterioles (EA) by 33 +/- 3 (P < 0.01) and 33 +/- 5% (P < 0.01), respectively. The addition of diltiazem altered neither RPF nor vessel diameters. Administration of AVPX recovered RPF, AA, and EA diameters. When hydronephrotic kidneys were pretreated with thromboxane (Tx) inhibitors, AVP reduced RPF by 62 +/- 5% (P < 0.01) and constricted AAs and EAs by 26 +/- 2 (P < 0.01) and 17 +/- 3% (P < 0.05), respectively. Under Tx blockade, diltiazem partially reversed the AVP-induced reduction in RPF and restored the decrements in AA diameter. Subsequent addition of AVPX returned RPF and EA diameter. Our data indicate that AVP elicits substantial renal microvascular constriction and suggest that AVP stimulates Tx production in hydronephrotic kidneys, thereby altering renal vascular responsiveness to this peptide.