[Effect of adrenaline on cyclic nucleotide concentration in the tissues of rats of different ages]

Content and the ratio of cAMP/cGMP in myocardium, liver tissue and sceletal muscle were similar in adult and old rats. Adrenaline (5 . 10(-6) M) caused more distinct increase in content of cAMP in the old animals. After treatment with NaF (0.01 M) the age differences in the cAMP content were observed only in the heart muscle. Adrenaline appears to activate most effectively adenylate cyclase in tissues of old rats; the enzyme is apparently responsible for enhanced sensitivity to the hormone in senile age.