Role of carbohydrate metabolism in hormonal regulation of spermatogenesis

In mammals the testis, the site of male germ cell development, can be\ndivided morphologically in two cellular compartments, viz. the seminiferous\ntubules and the interstitial tiSsue between the tubules. The seminiferous\ntubules contain developing germ cells and Sertoli cells and are surrounded\nby a boundary layer of myoid cells. The interstitial tissue contains Leydig\ncells, blood.and lymph vessels, nerves and fibroblasts. In intact animals\ntransfer between the two compartments is restricted (Setchell & Waites,\n1975). A harrier to substances of widely varying molecular size is formed,\nbecause the Sertoli cells which line the seminiferous tubules are closely\nconnected by elaborate tight junctions between the basal parts of the cells\n(blood-testis harrier). Insome species a second, less effective harrier is\nformed by myoid cells which surround the seminiferous tubules (Fawcett,\n1975) (Figure I. 1).\nDevelopment of gerrn cells starts with the spermatogonial stem cells\nwhich are located at the basis of the Sertoli cells in the seminiferous\ntubules but outside the blood-testis barrier (basal compartment). After\nseveral mitotic divisions of the spermatogonia, preleptotene spermatocytes\ndevelop which synthesize DNA) so that they finally contain twice the\namount of DNA present in non-dividing somatic cells. In the propbase following\nthe preleptotene stage, rearrangement of the chromosomal material\ntakes place as a preparatien for the first meiotic division. The meiotic\npropbase is subdivided in the leptotene, zygotene, pachytene and diplotene.\nDuring the leptotene and zygotene tight junctions are formed between\nthe Sertoli cells at the basal side of the germ cells and subsequently the\ntight junctions at the luminal side are dissolved (Russell, 1980). In this\nway the germ cells are transported through the blood-testis harrier to the\nlumen of the seminiferous tubules (adluminal compartment) without disruption\nof the blood-testis harrier. The propbase is foliowed by the first meiotic\ndi vis ion, and the generated secondary spermatocytes_ go quickly through\nthe Second meiotic division, without synthesis of DNA.