Major proteins secreted by the epididymis of Lacerta vivipara. Identification by electrophoresis of soluble proteins.

During their period of activity, epithelial cells of the lizard epididymis produce secretory granules containing highly insoluble central cores of protein nature (protein H). After centrifugation of the epididymal fluid at 15 000 X g, major soluble proteins were separated in the supernatant by polyacrylamide gel electrophoresis. These proteins were labelled by repeated injections of [3H]leucine into animals. In cylindrical gel electrophoreses, labelled proteins migrated as a single band towards the anode in the presence of SDS, and as two separate bands without SDS. The fastest component obtained in non-denaturing conditions was designated protein L. In two-dimensional gel electrophoreses, the two bands separated in the first dimension both migrated to the same position in the second dimension with SDS. Consequently it may be assumed that protein L is a monomer (molecular weight about 16 000-20 000) able to aggregate into polymers which can be dissociated with SDS. It was proved by hemicastration experiments that these soluble proteins did not originate from the testis. In addition, they were detected after short incubation of epididymal tissues in the presence of [3H]leucine. It is concluded that these proteins are elaborated by epithelial cells of the epididymis and discharged into the lumen. A possible role in the physiology of spermatozoa is briefly discussed.