Cyclic nucleotide (cAMP and cGMP) contents in the tissue of the heart, liver,lung, spleen, kidney and brain of rats were measured by radioimmunoassay to investigate the effect of Bac - chun - fang on aging peocess after oral administration. The results were as follows:1 )cAMP content of the heart, liver and lung in old rats of the treated groups were reduced, while those of the kidney and brain were increased; 2 ) cGMP contents of the liver, lung and spleen in the tested groups were decreased, while those o...