Functional relationships of the mammalian testis and epididymis.

The development of knowledge in four areas of research in male reproductive physiology of particular interest is reviewed. The concept of the blood-testis barrier (BTB), which arose following dye exclusion from the seminiferous tubules, has now been established as the differential transfer from interstitial fluid to tubular and rete testis fluids of molecules of physiological importance. The composition of fluid collected mostly from the rete testis of several species, not only reflects the nature of the barrier, but also the secretory capacity of the Sertoli cell. The functional significance of the transfer of molecules into testicular fluid and the composition of the fluid flowing into the epididymis are discussed. Sertoli cells establish the structural basis of the BTB during puberty and divide the seminiferous epitheliuym into basal and adluminal compartments. The Sertoli cell is the prime target for follicle stimulating hormone (FSH). The responses evoked by FSH are discussed, including special mention of androgen binding protein (ABP) and the protein hormone, 'inhibin', with FSH-suppressing properties. The control of FSH in the lamb is mentioned including new evidence to support a tubular source of a feedback agent with significance during the impuberal stage. Finally, some of the biochemical properties of the epididymis and its fluid contents are reviewed and the epididymal sperm are identified as the site of the antifertility action of the 6-chloro-6-deoxy sugars.