Major proteins secreted by the epididymis of Lacerta vivipara. Isolation and characterization by electrophoresis of the central core.

Lizard epididymis produces large secretory granules (6 micrometer) which are discharged and mix with the spermatozoa. They consist of a dense central core and a peripheral vacuole. Central cores were prepared by two means: (1) homogenization of epididymal cells than isolation of a granular fraction by centrifugation on a discontinuous sucrose density gradient as a final step, and (2) collection of epididymal fluid containing both granules and spermatozoa, and separation of these elements by several steps of low speed centrifugations and washings. Purity of the different fractions was checked by microscopy. After complete dissolution in Triton X-100 (2.5%), the fractions containing central cores were submitted to SDS-polyacrylamide gel electrophoresis (15% acrylamide bisacrylamide). When apparently free from surrounding material, the dissolved central cores analyzed by electrophoresis showed only a main band representing a single protein (or a small group of proteins) of relative low mobility (molecular weight about 70 000). Other more mobile proteins have been identified in less purified fractions. They probably originate from the peripheral vacuole but this point is still under investigation. These two types of proteins do not originate from plasma or testis. Their androgen dependence is discussed.