Bajpai M, Gupta G, Setty B S
Division of Endocrinology, Central Drug Research Institute, Lucknow, India.
Eur J Endocrinol. 1998 Mar;138(3):322-7. doi: 10.1530/eje.0.1380322.
A study was undertaken to estimate the activities of the key enzymes of glycolysis, the pentose phosphate pathway and the tricarboxylic acid (TCA) cycle in purified rat spermatocytes and spermatids, which have been shown to die in glucose-containing medium and require lactate/pyruvate for maintaining normal ATP concentrations. The aim was to elucidate the changes in the glycolytic and oxidative potential of germ cells undergoing meiosis. Pachytene spermatocytes and round spermatids from adult rat testis were purified to approximately 90% purity by trypsin digestion followed by a combination of centrifugal elutriation and Percoll density gradient centrifugation. After the purity and viability of these cells had been established, their contents of hexokinase, phosphofructokinase, lactate dehydrogenase (LDH) and LDH-X of glycolysis, glucose 6-phosphate dehydrogenase of the pentose phosphate pathway and citrate synthase, aconitase, malate dehydrogenase and 2-oxoglutarate dehydrogenase of the TCA cycle were estimated. These enzymes were also estimated in epididymal spermatozoa for comparison with the testicular germ cells. The results indicate greater activity of glycolytic and pentose phosphate pathway enzymes in spermatocytes than in spermatids, which exhibited greater activity of TCA cycle enzymes than the former. The difference in activity was statistically significant for most of the enzymes studied. In contrast, spermatozoa exhibited markedly greater activity of glycolytic enzymes and significantly lower activity of pentose phosphate pathway and TCA cycle enzymes than did the testicular germ cells. We conclude that the unusual dependence of spermatids exclusively on lactate may be due to their lower glycolytic potential, whereas spermatocytes with comparatively greater glycolytic activity have an intermediate dependence on lactate and are therefore able to utilise lactate, pyruvate, or both, while retaining a better ability to utilise glucose. Spermatozoa with the greatest glycolytic potential and the lowest TCA cycle activity appear to be 'programmed' to utilise exclusively glucose/fructose for energy.
开展了一项研究，以估算纯化的大鼠精母细胞和精子细胞中糖酵解、磷酸戊糖途径及三羧酸（TCA）循环关键酶的活性。已证实这些细胞在含葡萄糖的培养基中会死亡，且需要乳酸/丙酮酸来维持正常的ATP浓度。目的是阐明减数分裂过程中生殖细胞糖酵解和氧化潜能的变化。通过胰蛋白酶消化，随后结合离心淘析和Percoll密度梯度离心，将成年大鼠睾丸中的粗线期精母细胞和圆形精子细胞纯化至纯度约为90%。在确定这些细胞的纯度和活力后，估算了它们糖酵解过程中的己糖激酶、磷酸果糖激酶、乳酸脱氢酶（LDH）和LDH-X、磷酸戊糖途径的葡萄糖6-磷酸脱氢酶以及TCA循环的柠檬酸合酶、乌头酸酶、苹果酸脱氢酶和2-氧代戊二酸脱氢酶的含量。还估算了附睾精子中这些酶的含量，以便与睾丸生殖细胞进行比较。结果表明，精母细胞中糖酵解和磷酸戊糖途径酶的活性高于精子细胞，而精子细胞中TCA循环酶的活性高于精母细胞。所研究的大多数酶的活性差异具有统计学意义。相比之下，精子中糖酵解酶的活性明显高于睾丸生殖细胞，而磷酸戊糖途径和TCA循环酶的活性则明显低于睾丸生殖细胞。我们得出结论，精子细胞仅对乳酸的异常依赖可能是由于其较低的糖酵解潜能，而糖酵解活性相对较高的精母细胞对乳酸有中度依赖，因此能够利用乳酸、丙酮酸或两者，同时保留更好的利用葡萄糖的能力。具有最高糖酵解潜能和最低TCA循环活性的精子似乎“被设定”为仅利用葡萄糖/果糖作为能量来源。
