J. A. Grootegoed

REGULATION OF SURVIVAL OF GERM CELLS BY LACTATE SUPPLY FROM SERTOLI CELLS

Sertoli cells secrete many compounds, but none of them has been shown to influence germ cells directly. We observed, by phase contrast microscopy, a positive effect of exogenous lactate on the survival of pachytene spermatocytes and round spermatids, obtained from 32-day-old rats. Addition of 6 mM DL-lactate to the medium stimulated the oxygen consumption (two-fold) as well as [sHH]uridine and [l*C]leucine incorporation (five-fold) in spermatocytes and spermatids. No significant effects of glucose (3.3 mM) have been shown in the absence or presence of lactate. After preincubation of spermatocytes and spermatids without lactate but with glucose for 5 h or 70 min respectively, the incorporation of [:?!5]methionine was not restored after addition of lactate. This indicates that in the absence of lactate, germ cells are irreversibly damaged. It is concluded that lactate is essential for survival of these germ cells. Isolated spermatocytes and spermatids were active in [3H]uridine incorporation in the presence of glucose (3.3 mM) when they were co-cultured with Sertoli cells. The incorporation of [Hluridine in RNA of spermatocytes in the presence of Sertoli cells could be stimulated by glucose and was maximal at glucose concentrations higher than 0.5 mM, when measured within two hours. The survival of pachytene spermatocytes in cultures of seminiferous tubules was dependent on the presence of glucose. All spermatocytes were degenerated (phase contrast microscopy) after 24 h incubation in medium without glucose. The secretion of lactate by Sertoli cells in 2.5 h was linearly dependent on the glucose concentration from 0 to 0.5 mM and was maximal at 1.5 mM glucose. These studies demonstrate that the activity and survival of germ cells can be regulated by supply of lactate from Sertoli cells. The lactate secretion of pure Sertoli cells, isolated from irradiated rats, could be stimulated (twoto four-fold) by FSH (5 pg/ml). No effects of testosterone have been shown. These results suggest that lactate plays a role in the indirect hormone action on germ cells.