Administration of exogenous testosterone in the adult rat and its effects on reproductive organs, sex hormones and body-weight.

The present experiment was performed to observe the effects produced by high dose of a testosterone ester on the reproductive organ and body weight changes in the adult rat, and to correlate these effects with the serum hormone changes. The present study has used the benzoate ester of testosterone (Testosterone benzoate, TB) in the adult male rat (300-350 g). The aim was to co-relate the reproductive organ and body-weight changes with changes in the serum hormone levels following the administration of the ester. TB was injected i.p. for five (5) consecutive days at a dose of 100 mg/kg body-weight. The control rats were injected with vehicle (arachis oil) at the same dose. The rats were killed on the 6th, 12th, 18th, 24th and 36th days. Controls for only the 6th and 36th days were kept. Reproductive organ weight, body-weight and testosterone (T) levels in serum and testis together with serum FSH and serum LH levels were observed. The testes weights remained similar (p < 0.05) to those in the control rats until the 18th days and were reduced on the 36th day. The epididymis weights were not changed until the 36th days, while the androgen-dependent seminal vesicle and ventral prostate weights were increased (< 0.05) compared to those in the control rats. The body-weights remained unchanged at the 6th day but were significantly (p < 0.05) decreased on the 36th day. The serum testosterone (ST) concentrations were highly raised on the 6th day, came at the control level on the 18th day and were significantly decreased (< 0.05) on the 36th day. The testicular testosterone (TT) content remained significantly lower (p < 0.05) from the 6th to the 36th days post-injection. The serum LH and FSH levels also remained significantly lower (p < 0.05) throughout the treatment period. It appears that the elevated serum T levels exerted dual effect in the adult rats, namely, enhanced growth of the androgen-dependent organs and an inhibition over the hypothalamo-pituitary-testicular axis. Inhibition of the said axis was evident by the lower levels of the serum LH and FSH; probably due to this, the TT-content remained all through lower, and perhaps this low TT-content for the long period had led to the low testis weights (p < 0.05) on the 36th day. This experiment therefore, demonstrates the effects of exogenous androgen administration in the adult male rat physiology.