Endogenous nitric oxide is not involved in acute parathyroid hormone-induced hypotension in rat: effect of hypertension and hypoparathyroid status.

The present study investigated the acute hypotensive effect of parathyroid hormone (PTH) in anesthetized adult spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats. Furthermore, in order to determine the possible contribution of nitric oxide (NO), a mediator of endothelium-dependent vasorelaxation, hypotensive responses to PTH were obtained in the presence of NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthesis. The hypotensive effect of PTH (expressed as % of baseline blood pressure) was similar for the two strains. In the presence of L-NAME (18.5 mumol/kg), both strains demonstrated a similar hypotensive response to PTH, indicating that the hypotensive response to PTH is NO-independent.