Androgenic control of the cyclic AMP-dependent protein kinase isoenzymes of the rat epididymis.

The specific activity of the type I and type II isoenzyme forms of the cAMP-dependent protein kinase (EC 2.7.1.37) in the caput epididymidis of the intact rat was less than that of the caudal region while the isoenzyme ratio (type II:type I) of the former was greater than that of the latter, with type II being the predominant form in both regions. By 7 days after castration, the specific activities in both regions had decreased to the same levels. The isoenzyme ratio of the caudal region increased to that of the caput region which remained unchanged after castration. The change in the isoenzyme ratio in the caudal region was mainly due to loss of the type I isoenzyme. The castration effects were reversed by testosterone administration.