Prostaglandin E2 is an inhibitor of adenylate cyclase in rabbit proximal tubule

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Abstract
Prostaglandin E1 and E2 (PGE) antagonize the phosphaturic effect of parathyroid hormone (PTH), but do not alter the phosphaturia evoked by adenosine 3',5'-cyclic monophosphate (cAMP) analogues. These findings support the idea that PGE interfere with activation of adenylate cyclase in the renal proximal tubule. We tested this hypothesis in the rabbit renal proximal straight tubule (PST). In the PST, adenylate cyclase was activated by PTH (Km = 10(-9) M PTH), but not by PGE2, which attenuated the activation of adenylate cyclase by PTH. The inhibition by PGE2 of PTH action was prevented by pertussis toxin, which deactivates the regulatory aggregate, Ni. In the PST, PGE2 also attenuated the activation of adenylate cyclase by cholera toxin. The inhibitory effect of PGE2 was selective; PGE2 did not inhibit activation of adenylate cyclase in glomeruli, but it inhibited the enzyme in proximal convoluted tubules (PCT) and PST. We conclude that PGE2 inhibits adenylate cyclase in rabbit proximal tubule. We propose that this action may, in part, regulate transport function in vivo.

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