Patologìâ (Jan 2019)
The state of reproductive organs of young and aged male rats with the prolonged administration of letrozole and after its withdrawal
Abstract
Aim. Study of the reproductive organs after long-term administration of letrozole, the steroid aromatase inhibitor, followed by its withdrawal in young male rats and ones with age-related involution of reproductive organs. Material and methods. The experiments were carried out on Wistar rats with an initial age of 5 months and 15 months, which were gavaged with letrozole every other day at a dose of 1 mg/kg bw for 3 months and then 2 months following its discontinuation. The blood plasma testosterone and estradiol levels were measured by immunoassays. The spermatozoa contents in epididymis were calculated. The testicles and accessory sexual glands were weighed, and morphology of gonads and ventral prostate was studied. The results of the study were compared with those of control animals of corresponding age. Results. As the result of letrozole treatment, the ratio of testosterone and estradiol levels in blood plasma of aged rats increased. The spermatozoa content in epididymis rose up by on the average 28 %. The histological study revealed functional activation of Leydig cells, a significant retardation of involutive changes of their number and morphology. Some Leydig cells demonstrated the signs of functional exhaustion. Letrozole exerted an increase of relative weight of the coagulation gland by an average of 40 %, seminal vesicles by 31 %, and ventral prostate by 33 % compared with those of control animals. Two months after letrozole withdrawal, there were no signs of difference between letrozole-treated and control animals. In young rats, the effects of letrozole were almost not detectable. Conclusions. Letrozole administration to male rats with age-related involution of the reproductive system increases testosterone/estradiol ratio in blood plasma, the spermatozoa contents in epididymises and the weights of androgen-dependent accessory sexual glands. This is accompanied by slowing down of age-related changes of the gonad morphology and prostate gland. Letrozole-induced reproductive effects are reversible.
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