The Movement of Fluids and Substances in the Testis

Abstract

Three aspects of the control of movements of fluids and substances into, out of and inside the testis are discussed: the tubular barrier, the interstitial extracellular fluid and the testicular blood vessels. The functional basis for the tubular barrier is twofold; there are significant differences in the concentration of many substances inside and outside the tubules and marker substances enter or leave the tubular fluid at widely different rates, depending on lipid solubility and the presence of specific carrier systems. The anatomical basis for this barrier appears to be the specialized junctions between adjacent pairs of Sertoli cells. The barrier develops only at puberty, as the first cells undergo meiosis, but the development may not be as sudden as previously believed. The barrier breaks down after efferent duct ligation when spermatogenesis is disrupted. Techniques for measuring the volume, the turnover rate, the composition and fate of the interstitial extracellular fluid are described, and the unsatisfactory features of the presently available techniques for collecting this fluid for analysis are emphasized. There is a relationship between the fluid in the testis and lymph from vessels in the spermatic cord and lymph may be important for the transport of hormones to the general circulation in some circumstances and to other organs close to the testis. The testicular blood vessels display certain unusual features, a very high susceptibility to the toxic effects of cadmium salts, a high level of alkaline phosphatase activity in all endothelial cells but only after puberty and a high level of gamma-glutamyl transpeptidase in the endothelial cells of the arterioles and the testicular artery. These same cells are the site for a specific transport system for leucine and phenylalanine, with kinetic characteristics similar to the system in brain. Flow of blood may limit hormone secretion by the aspermatogenic testis, but diffusion limitation may also be important under some circumstances. A fuller understanding of the ways in which substances move around in the testis, particularly how they cross the endothelial cell layer or penetrate into the tubules, will be important for a better appreciation of testicular function.

Interactions between nutrition and reproduction in the management of the mature male ruminant

“…The relative volume of blood and lymph vessels was not affected by diet in the study by Hö tzel et al (1998), but their absolute volumes increased or decreased as a function of the change in testicular size. These changes in the vasculature and the associated changes in blood flow, accommodate the transport of testosterone to the peripheral circulation (Setchell, 1986 and1990). Thus, the present data are in agreement with a previous nutritional study in mature rams (Setchell et al, 1965) and suggest that total blood flow was affected while there was probably little or no change in blood flow per unit mass of testis.…”

The blood‐testis barrier and sertoli cell junctions: Structural considerations

“…Furthermore, the data are consistent with the observation that the size of the lumen continues to enlarge well beyond the onset of spermatogenesis and pubertythat is, up to the 60th day after birth in rats (Tindall et al, 1975). As pointed out by Setchell(1986), a progressive and delayed development of the barrier is further supported by the finding that the concentration of androgen binding protein (ABP) in the epididymis-"a biochemical marker of formation of the barrier"-also continues to rise beyond the onset of spermatogenesis (Tindall et al, 1975). These observations suggest that fluid secretion by Sertoli cells may be related to the competence of the barrier.…”

Infertility with defective spermatogenesis and hypotestosteronemia in male mice lacking the androgen receptor in Sertoli cells

“…The columnar and convoluted structure of Sertoli cells provides physical support for spermatogonia undergoing mitosis, spermatocytes undergoing meiosis, and spermatids undergoing spermatogenesis to become spermatozoa (35). Sertoli cell-mediated environmental interactions are essential in the creation of the blood-testis barrier and maintenance of the unique microenvironment within the seminiferous tubule required for germ cell development (36). However, an earlier study showed that in vitro cultured Sertoli cells were unable to fully respond to some treatments, including androgen (37).…”