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During incubation of fragments of seminiferous tubules in the absence of glucose, pachytene spermatocytes and round spermatids died within 24 h, while Sertoli cells were still viable. The germ cells survived for at least 72 h in seminiferous tubule fragments which were incubated in the presence of glucose. Lactate rather than glucose is essential for [3H]uridine incorporation and survival of isolated pachytene spermatocytes. However, if the spermatocytes were incubated in the presence of Sertoli cells, glucose maintained the incorporation of [3H]uridine into the germ cells. Sertoli cells secreted lactate in the presence of glucose and the lactate secretion was stimulated 2--4-fold by FSH. It is concluded that the activity and survival of pachytene spermatocytes in vitro can be regulated by the supply of lactate from Sertoli cells.

Sertoli cells were obtained from 3\p=n-\6-week-oldrats, which were sterile after prenatal irradiation. The production of lactate by these Sertoli cells, measured 24\p=n-\48h after isolation during incubation in the absence of hormones, increased with age of the rats from 3 to 6 weeks. At all ages investigated, the production of lactate was enhanced in the presence of FSH plus testosterone, but the stimulation was most pronounced at 4 weeks of age. Lactate production was increased by FSH alone but testosterone had no effect in the presence or absence of FSH. Sertoli cells from 4-week-old rats produced both pyruvate and lactate, which accumulated in the incubation medium in a ratio of 1:4. The stimulation of the production of pyruvate and lactate by FSH was dose\x=req-\ dependent (ED50 at~10 ng NIH-FSH-S13/ml). The production of pyruvate and lactate was stimulated 2-fold by insulin, 4-fold by FSH and > 6-fold by dibutyryl cyclic AMP (in the presence of 3-isobutyl-1-methylxanthine). The effects of FSH (0\m=.\5\ g=m\ g NIH-FSH-S13/ml) and insulin (5 \g=m\g/ml) were not additive.Leucine incorporation into isolated pachytene spermatocytes and round spermatids was stimulated by exogenous pyruvate and lactate in a dose-dependent way : maximal incorporation was obtained with 0\m=.\2 mM-pyruvate or 2 mM L-lactate. Spent medium from incubated Sertoli cells (from 4-week-old rats) stimulated the leucine incorporation into isolated pachytene spermatocytes and round spermatids 4\p=n-\8-fold.This effect could be explained by the amounts of pyruvate and lactate present in the spent medium. It is suggested that pyruvate and lactate are major products from Sertoli cells which can support synthetic activities in germ cells, and the present results indicate that pyruvate and lactate may play a role in the hormonal regulation of spermatogenesis.

We studied the presence of donor-specific T lymphocytes in explanted human cardiac valve allografts in vivo. From five of seven explants we propagated lymphocyte cultures in an interleukin-2 conditioned medium. Phenotyping revealed the presence of T-cell receptors in more than 95% of the lymphocytes obtained in each culture. Donor-specific cytotoxicity was demonstrated in three patients with known HLA status of the donor. Cytotoxicity was directed against only HLA class I in one patient, and against class I and/or class II in the others. These results indicate that donor-specific cellular reactivity can be induced by transplantation of human cardiac valve allografts.

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