Slices of the rat epididymis were incubated with [32P]orthophosphate. Analysis of the radioactive proteins in the medium by two-dimensional gel electrophoresis and autoradiography revealed 6-phosphorylated secretory proteins from the epididymis of adult rats: Mr = 62 000; 66 000; 76 000; 68 000; 19 000 and 20 000. Studies of the epididymides of immature and 7-day-castrated adult rats indicated that these phosphorylated secretory proteins were controlled by androgens.

Summary. 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 level. 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.

Rat hexokinases fro caput sperm (immature) and caudal sperm (mature) were investigated. The hexokinases from both sources were studied by DEAE-cellulose column chromatography and by cellulose acetate electrophoresis. The specific activity of caput sperm hexokinase was not significantly different from that of the caudal sperm enzyme. Spermatozoa possess two isozymes of hexokinase. Type I hexokinase was the predominant type in caput sperm whereas the sperm type of hexokinase was predominant in caudal sperm. Hexokinase types II and III were absent in both extracts.