Subcellular distribution and circadian rhythm of some glycolytic enzymes in rat testis

An update on the role and potential mechanisms of clock genes regulating spermatogenesis: A systematic review of human and animal experimental studies

Circadian clocks can be traced in nearly all life kingdoms, with the male reproductive system no exception. However, our understanding of the circadian clock in spermatogenesis seems to fall behind other scenarios. The present review aims to summarize the current knowledge about the role and especially the potential mechanisms of clock genes in spermatogenesis regulation. Accumulating studies have revealed rhythmic oscillation in semen parameters and some physiological events of spermatogenesis. Disturbing the clock gene expression by genetic mutations or environmental changes will also notably damage spermatogenesis. On the other hand, the mechanisms of spermatogenetic regulation by clock genes remain largely unclear. Some recent studies, although not revealing the entire mechanisms, indeed attempted to shed light on this issue. Emerging clues hinted that gonadal hormones, retinoic acid signaling, homologous recombination, and the chromatoid body might be involved in the regulation of spermatogenesis by clock genes. Then we highlight the challenges and the promising directions for future studies so as to stimulate attention to this critical field which has not gained adequate concern.

Effect of dexamethasone on testicular enzymes of the Embden-Meyerhof and pentose-phosphate pathways

The influence of dexamethasone on the specific activities of testicular enzymes involved in the Embden-Meyerhof and pentose-phosphate pathways was studied in pre-pubertal, pubertal and adult rats. All of the enzymes showed a decrease in specific activity after dexamethasone treatment, an effect which was most drastic in pre-pubertal animals. After cessation of treatment, the specific activity of all the enzymes reverted to normal levels, except for glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the pre-pubertal group.

Effect of adrenalectomy and dexamethasone treatment on testicular enzymes involved in carbohydrate metabolism

The effect of adrenalectomy on specific activities of testicular hexokinase, 6-phosphofructokinase, pyruvate kinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and glycogen concentration have been studied. A general increase in specific activities of all enzymes was seen after adrenalectomy in rats of all ages studied. However, lactate dehydrogenase activity and glycogen concentration in pre-pubertal rats alone were depleted with no alteration in pubertal and adult animals. This was accompanied by increased prolactin titres, but gonadotrophins and testosterone were unaltered. Dexamethasone treatment returned all enzyme activities and hormonal profiles to normal.

Specific effect of the thyroid on testicular enzymes involved in carbohydrate metabolism. I. Hypothyroidism

The effect of thyroidectomy (Tx) on some key enzymes involved in glycolysis and the HMP-shunt pathway were studied in the testis of pre-pubertal, pubertal and adult rats. Hexokinase (HK) and phosphofructokinase (PFK) did not show any significant change in activity after Tx. However, pyruvate kinase (PK) activity was reduced after Tx in the testis of pre-pubertal animals although in pubertal and adult rats it was not affected. Both glucose-6-phosphate dehydrogenase (G6P-DH) and 6-phosphogluconate dehydrogenase (6-PG-DH) activities were reduced after Tx and thyroxine (T4) replacement brought both enzyme activities back towards normal. The possible effect of the thyroid on testicular steroidogenesis acting through the HMP-shunt is discussed.

Specific effect of thyroid hormone on testicular enzymes involved in carbohydrate metabolism. II. Hyperthyroidism

The influence of thyroxine on some of the key enzymes involved in glycolytic and pentose phosphate pathways in the testes of pre-pubertal; pubertal and adult rats was studied. Thyroxine-induced (25 micrograms/100 g body weight) hyperthyroidism for 1 month resulted in no change in either hexokinase (EC 2.7.1.1) or 6-phosphofructokinase (EC 2.7.1.11) activity in the testes of rats in any age group studied. However, pyruvate kinase (EC 2.7.1.40) activity was reduced significantly in the pre-pubertal and pubertal rats. Both glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) activities were markedly increased after thyroxine treatment. Withdrawal of hormone treatment resulted in reversion of enzyme activities towards normal. The results suggest that thyroxine has an age-dependent, specific effect over testicular pyruvate kinase activity. Thyroid hormone may have a direct control over the pentose phosphate pathway in the testis.