Role of carbohydrate metabolism in hormonal regulation of spermatogenesis

In mammals the testis, the site of male germ cell development, can be divided morphologically in two cellular compartments, viz. the seminiferous tubules and the interstitial tiSsue between the tubules. The seminiferous tubules contain developing germ cells and Sertoli cells and are surrounded by a boundary layer of myoid cells. The interstitial tissue contains Leydig cells, blood.and lymph vessels, nerves and fibroblasts. In intact animals transfer between the two compartments is restricted (Setchell & Waites, 1975). A harrier to substances of widely varying molecular size is formed, because the Sertoli cells which line the seminiferous tubules are closely connected by elaborate tight junctions between the basal parts of the cells (blood-testis harrier). Insome species a second, less effective harrier is formed by myoid cells which surround the seminiferous tubules (Fawcett, 1975) (Figure I. 1). Development of gerrn cells starts with the spermatogonial stem cells which are located at the basis of the Sertoli cells in the seminiferous tubules but outside the blood-testis barrier (basal compartment). After several mitotic divisions of the spermatogonia, preleptotene spermatocytes develop which synthesize DNA) so that they finally contain twice the amount of DNA present in non-dividing somatic cells. In the propbase following the preleptotene stage, rearrangement of the chromosomal material takes place as a preparatien for the first meiotic division. The meiotic propbase is subdivided in the leptotene, zygotene, pachytene and diplotene. During the leptotene and zygotene tight junctions are formed between the Sertoli cells at the basal side of the germ cells and subsequently the tight junctions at the luminal side are dissolved (Russell, 1980). In this way the germ cells are transported through the blood-testis harrier to the lumen of the seminiferous tubules (adluminal compartment) without disruption of the blood-testis harrier. The propbase is foliowed by the first meiotic di vis ion, and the generated secondary spermatocytes_ go quickly through the Second meiotic division, without synthesis of DNA.