Effect of thyroxine treatment on epididymal carbohydrate metabolism in the pubertal rat.

The influence of thyroxine treatment on key enzymes involved in the glycolytic and HMP shunt pathways was studied in the caput, corpus and cauda epididymides of pubertal rats, and related to the serum hormone profile. The activity of 6-phosphofructokinase and pyruvate kinase was significantly increased in all 3 segments of the epididymis, but the HMP shunt pathway was suppressed. Thyroxine treatment was found to depress the serum levels of testosterone, LH and FSH, although an increase in prolactin levels was observed. Withdrawal of hormone treatment resulted in the restoration of normal activity of 6-phosphofructokinase and pyruvate kinase and restoration of normal serum hormone levels. However, the activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase increased following withdrawal of treatment. It is concluded that hyperthyroidism exerts an influence on epididymal enzymes involved in carbohydrate metabolism.