Relaxation of renal arterioles by parathyroid hormone and parathyroid hormone-related protein.

The effects of parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) on renal arteriolar tone and proximal tubule adenylate cyclase were examined. In both afferent and efferent arterioles, PTH produced concentration-dependent relaxation of norepinephrine-induced tone with EC50 values of 8.7 and 9.9 nmol/l, respectively. PTHrP also produced relaxations that were indistinguishable from PTH. In proximal convoluted tubules PTH and PTHrP stimulated adenylate cyclase to the same extent and with similar potencies. The PTH antagonist, bPTH(7-34), totally blocked PTH-induced arteriolar relaxation but had no effect on proximal tubule adenylate cyclase. The results demonstrate that PTH and PTHrP are potent relaxants of glomerular arterioles and that PTH receptors present on the renal microvasculature may differ from those present on proximal tubules.