Localization of Transferrin and Transferrin Receptors in Rat Testes

Abstract

One of the major proteins secreted by rat Sertoli cells in culture is a transferrin-like protein. The amount of testicular transferrin in fluids isolated from the testis was quantitated by the use of a radioimmunoassay and the location of transferrin and transferrin receptors in the testis determined by indirect immunofluorescence. Seminiferous tubule fluid rete testis fluid, and testicular lymph were collected from rat testes and contained 141, 47 and 3.7 mg transferrin/ml of fluid, respectively. Serum contained 3.7 mg/ml transferrin. Paraffin sections of rat testis were incubated with rabbit anti-rat transferrin, biotinylated goat anti-rabbit and fluorescein-conjugated avidin. Immunoreactive transferrin was thus localized on the proacrosome and nuclear cap of developing spermatids. Late spermatids showed transferrin over the entire region of the head but mature testicular spermatozoa exhibited little fluorescence. The interstitial tissue between seminiferous tubules fluoresced brightly, indicating a large amount of transferrin in this area. By pretreating sections with rat transferrin, the receptor for the protein was localized on and in spermatocytes and early round spermatids. Dividing germ cells were brightly fluorescent.