Maturation dependent decline of adenylate cyclase in rabbit red blood cell membranes

Adenylate cyclase (EC 4.6.1.1) was studied in membrane preparations of reticulocyte-rich blood obtained from phenylhydrazine-treated rabbits and compared to that of untreated animals. Basal and fluoride-stimulated activities were decreased 2- and 4-fold, respectively, during the process of maturation. Catalytic parameters such as time course, protein, ATP, Mg2+ concentration curves and Km have been determined and were found to be similar in the reticulocyte and the erythrocyte. Adenylate cyclase was sensitive to GTP, 5'-guanylyl imidodiphosphate, prostaglandin E1 and prostaglandin E2. Activation by prostaglandin E1 was higher than that produced by prostaglandin E2. Only additive effect was found when 5'-guanylyl imidodiphosphate or GTP was added to hormone-stimulated activity. The sensitivity of the enzyme to these effectors was decreased over the transition reticulocyte-erythrocyte. In either cell the enzyme was not activated by catecholamines (epinephrine, norepinephrine, isoproterenol).