SYNTHESIS, CHARACTERIZATION AND HORMONAL-REGULATION OF EPIDIDYMAL PROTEINS DURING POSTNATAL-DEVELOPMENT OF THE MOUSE

Maturation of mammalian spermatozoa depends on their interactions with epididymal proteins. The incorporation of S-35-methionine into these proteins was investigated by in vitro incubation of tissue minces from the mouse epididymis at different ages of postnatal development. The greatest amount of incorporation per wet weight of tissue was seen in 7 to 21-day-old mice. It decreased progressively during development wh ile the rate of proteins released into the medium remained almost cons tant until the adult state. Separation of labeled proteins on sodium d odecyl sulphate polyacrylamide gels followed by fluorography showed th at the great majority of secretory proteins synthesized in adult mouse epididymis could be recovered already from 7-day-old animals. Regiona l differences appeared at 21 days of age. These were marked by the sec retion of proteins characteristic of the proximal (26, 25, 20, 19 kDa) and distal (44, 29 kDa) epididymis. Analysis of cytosol and luminal f luid proteins from prepubertal and adult epididymis revealed a number of proteins of the same mobility as those synthesized and secreted in vitro. Among the luminal proteins which showed variations during devel opment and regional differences, four (29, 26, 20, 19 kDa) were charac teristics of the epididymis and three (88, 34, 13 kDA) comigrated with testicular components. Castration or estrogen treatment of prepuberta l mice for 4, 3 and 2 weeks inhibited or reduced the synthesis of the luminal proteins which appeared during postnatal development and/or pr esented regional differences. Testesterone replacement of castrated mi ce reversed this effect and induced the secretion of new proteins (37, 24 kDa). Combined administration of estrogen and testosterone to cast rated or intact prepubertal mice reduced the androgen effect on protei n synthesis. These results indicate that epididymal differentiation is characterized by the secretion of epididymal segment-specific and and rogen-regulated proteins which appear early during development even be fore the sperm arrival in the epididymis.