The renal parathyroid hormone receptor-adenylate cyclase system in vitro and in vivo

High affinity parathyroid hormone (PTH) receptors in chicken renal plasma membranes were identified and quantitated using bPTH((1-34) labeled by electrolytic iodination and purified by a membrane absorption procedure. Parallel studies of PTH-receptor binding and activation of adenylate cyclase indicated that these activities were coupled. The PTH sensitivity of the renal receptor-adenylate cyclase system was similar in vivo and in vitro (Km congruent to 20 nM), whereas a 'physiologic' concentration of circulating bPTH (1-34) infused into thyroparathyroidectomized/ultimobranchial-ectomized chickens was estimated to be at least 40 times lower. Small increments in cellular cyclic AMP levels are apparently sufficient to mediate actions of PTH on the kidney.