Lactate production by testicular fragments and isolated germinal cells at various stages of spermatogenesis was studied in aerobic and anerobic conditions. Several ATPase inhibitors were used to determine the role of ATPase activities in the control of aerobic lactate production. Aerobic glycolysis reached a high level in spermatogonia plus Sertoli cell and in primary spermatocyte populations. The activity was twice that found in early spermatids. Neither Na+-K+ ATPase nor mitochondrial F1 ATPase seemed to participate directly in the control of aerobic glycolysis. The uncoupling of oxidative phosphorylation revealed the potential role of F1 ATPase in providing ADP and P(i) for the glycolytic pathway. Lactate production was inhibited by quercetin in all the experimental conditions tested. Quercetin (100 microM) halted lactate production by the Sertoli cell plus spermatogonia population and by isolated primary spermatocytes. In spermatids, quercetin inhibited aerobic glycolysis only by 40%, even at higher concentrations. Only during the first meiotic prophase did quercetin inhibit the activity of a cytosolic Ca(2+)-Mg2+ ATPase. This ATPase was also inhibited by erythro-9-[3-3(hydroxynonyl)]adenine (EHNA), suggesting that a cytoplasmic dynein could be involved in the control of glycolysis in Sertoli cells, spermatogonia, and early primary spermatocytes.
In contrast with the transient pre-replicative increase in calmodulin (CaM) level observed in proliferative activated cells, postnatal development of rat testis was paralleled by 3 specific rises in CaM. The first one occurred between 5 and 10 days, coincident with the appearance and proliferation start of spermatogonia and Sertoli cells. Meiosis accomplishment and spermatid differentiation were paralleled by 2 additional rises, at 24 and 32 days, respectively. The plateau phase of testis growth was coincident with the appearance of maturating spermatids and spermatozoa in the germinal epithelium, and with a decrease in CaM content. Testicular DNA:g wet tissue ratio reached the highest level in 15-day-old rats and gradually decreased up to 35 days, when a constant level was reached. A similar level of Ca2+-CaMBPs was observed in 5- and 20-day-old rat testis. Although all subcellular fractions showed the ability to bind CaM in a Ca2+-dependent manner, CaM was mainly recovered in the nuclear and soluble fractions of adult and immature rat testis. Several Ca2+-CaMBPs with an apparent M(r) of 82, 75, 64, 19, and 14 kD were purified by affinity chromatography from pachytene primary spermatocyte nuclear matrix. Ca2+-CaMBPs showing an M(r) of 120, 78, 72, and 66 kD were also purified from the supernatant obtained after DNA and RNA hydrolysis of meiotic nuclei. Major cytosolic Ca2+-CaMBPs of primary spermatocytes showed an M(r) of 120, 84, 44, and 39 kD. The functions that these Ca2+-CaMBPs might have during the first meiotic prophase is discussed.
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