Defective Renal Adenylate Cyclase Response to Prostaglandin E2 in Spontaneously Hypertensive Rats

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We activated three known components of the adenylate cyclase system in renal membranes from spontaneously hypertensive (SHR) and Wistar-Kyoto(WKY) rats. The basal adenylate cyclase activity and responses to plasma membrane receptor activation by parathyroid hormone, isoproterenol and vasopressin were not different between the two strains. The response to prostaglandin E2 (PGE2), however, was less in the SHR than in the WKY at five, (P<0.05), 12 (P<0.01) and 16 (P<0.01) weeks of age. Activation of either the guanosine-5'-triphosphate (GTP) binding regulatory protein (N) with sodium fluoride (NaF) and guanyl-5'-yl-imidodiphosphate [Gpp(NH)p|, or the catalytic unit with manganese chloride (MnCI2) or forskolin were not different between the two groups. When the medullary and cortical plasma membrane adenylate cyclase responses were studied separately, the observed decreased response to PGE2 (of SHR) was found to be entirely in the cortex. Also, the NaF response was reduced in the cortical region of the 12-week-old rats, a finding suggesting a possibility of a post receptor defect. These results show that there is a defective renal adenylate cyclase response specific to prostaglandin E2 in SHR. This defect could be related to the development of hypertension, by changing the natriuretic and/or renal vasodilating effects of these prostaglandins.

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