The hypotensive effect of parathyroid hormone (PTH) was investigated in anesthetized adult spontaneously hypertensive (SHR) and Wistar-Kyoto rats. Furthermore, in order to determine the possible contribution of nitric oxide, a mediator of endothelium-dependent vasorelaxation, hypotensive response to PTH were obtained in the presence of NG- nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis. The hypotensive effect of PTH was significantly greater in SHR. Administration of L-NAME (5mg/kg) produced a lesser hypertensive response in SHR, suggesting that basal release of nitric oxide is decreased in SHR. In the presence of L-NAME, both strains demonstrated similar hypotensive response to PTH, indicating that hypotensive response to PTH is endothelium- and nitric oxide- independent.
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