Studies on the phosphodiesterase in various organs of rats and guinea-pigs of different ages and different sex.

The method of Butcher and Sutherland is used to determine the phosphodiesterase activity of various organ homogenates from rats and guinea-pigs of different age and sex. The different rat organs manifest great differences in their phosphodiesterase activity. Especially high phosphodiesterase activity is found in the adrenal gland and in the brain cortex. Sex is not found to be related to definite differences in the activity of the enzyme. In some organs age differences are established both in the phosphodiesterase activity and in the degree of its inhibition or activation by inhibitors and stimulators of the enzyme. It is assumed that in some organs age conditions changes not only in the general phosphodiesterase activity, but also in the ratio between its isoenzymes.