Mitogenic polypeptide of the mammalian seminiferous epithelium: biochemical characterization and partial purification.

Abstract

A mitogenic polypeptide, previously identified in Sertoli cells of the prepuberal mouse, now has been shown to exist in Sertoli cells of the adult mouse and in the seminiferous epithelium of several other mammalian species, including the rat, guinea pig and calf. The levels of this seminiferous growth factor (SGF) are not appreciably reduced in adult mouse testes following hypophysectomy. SGF purified from either the adult mouse or newborn calf seminiferous epithelium has a MW of 15,700 and a pI between 4.8 and 5.8, when exposed to denaturing conditions. SGF from these 2 mammalian species probably has few exposed hydrophobic domains and has a strong propensity to aggregate into multile, high MW species. A purification sequence based on these biochemical properties has enabled a > 350-fold enrichment of SGF activity from the calf seminiferous epithelium. The protocol involves a sequence of: ammonium sulfate precipitation; DEAE-cellulose ion exchange chromatography; gel filtration chromatogaphy on Bio-Gel P150 in 1.0 M ammonium acetate; hydrophobic chromatography on dodecyl agarose; and gel filtration chromatography in 6.0 M guanidine hydrocyhloride. Subsequent analysis of this purified preparation by SDS PAGE [sodium dodecyl sulfate-polyacrylmaide gel electrophoresis], followed by Ag staining, revealed .apprx. 7 polypeptides with MW between 14,000 and 20,000.