Adenylate Cyclase Responsiveness to Hormones

AVP (1 ,tM) stimulated adenylate cyclase activity in the terminal nephron segments only, i.e., the late portion of the distal convoluted tubule, the cortical and medullary portions ofthe collecting tubule (activity ratios 81, 51, and 97, respectively). As measured in one experiment, nearly one-halfmaximal responses were obtained with 0.1 IU/ml PTH or 0.3 ng/ml SCT in thick ascending limbs and with 1 nM AVP in collecting tubules, suggesting that enzyme sensitivity to hormones was well preserved under the conditions used in this study. A preliminary report of this research was presented at the VIIth International Congress of Nephrology, Montreal, June 1978. Dr. Gagnan-Brunette's current address is Hospital MIaisonneuve-Rosemont, Montreal, Canada. Dr. Gontcharevskaia's current address is Intitut Setchenov, Leningrad, U.S.S.R. Received for publication 9 July 1979 and in revised form 28 September 1979. J. Clin. Invest. (D The American Society for Clinical Investiga