Abstract 1. 1. The stimulation of the adenylate cyclase activity of isolated rat renal glomeruli by isoproterenol decreased during kidney maturation. A potentiation of the isoproterenol response by GTP was demonstrated in young and adult animals. 2. 2. Both KF and GPP(NH)P enhanced the enzyme activity under basal conditions in young and adult glomeruli. 3. 3. GTP had no significant effect upon the basal activity of the adenylate cyclase in glomeruli of 14-day old rat kidney while it had one in 21-day old and adult kidneys.