Plasma membrane transformations in spermatogenesis revealed by aldehyde fixatives containing tannic acid

Abstract

During spermatogenesis in the rat, the plasma membrane of the germ cell undergoes an abrupt change. The change appears in electron micrographs as a reduction of the electron density or as a reorganization of the outermost lamella of the unit membrane or both. The change occurs in the developmental stage between type B spermatogonia and early spermatocytes and is most clearly depicted in tissues fixed in glutaraldehyde—tannic acid followed by osmium tetroxide. The change is specific to germ cells and is not evident in Sertoli cells. The origin of the new type of germ cell plasma membrane has not been determined; however, it is noted that a population of thin-membrane cytoplasmic vesicles with asymmetrically stained membranes is present in spermatogonia before plasma membrane transformation but nearly absent in spermatocytes after plasma membrane transformation. The asymmetrical membranes of these cytoplasmic vesicles could be precursor material for the new, or transformed, type of germ cell plasma membrane. The plasma membrane changes noted above persist through spermatid development.