Effect of chronic administration of an aromatase inhibitor to adult male rats on pituitary and testicular function and fertility

Abstract

The aim of the present study was to evaluate the effects of the administration of a potent non-steroidal aromatase inhibitor, anastrozole, on male reproductive function in adult rats. As anastrozole was to be administered via the drinking water, a preliminary study was undertaken in female rats and showed that this route of administration was effective in causing a major decrease in uterine weight (P<0·02). In an initial study in male adult rats, anastrozole (100 mg/l or 400 mg/l) was administered via the drinking water for a period of 9 weeks. Treatment with either dose resulted in a significant increase (10%) in testis weight and increase in plasma FSH concentrations (P<0·01) throughout the 9 weeks. Mating was altered in both groups of anastrozole-treated rats, as they failed to produce copulatory plugs. Histological evaluation of the testes from anastrozole-treated rats revealed that spermatogenesis was grossly normal. In a more detailed study, adult rats were treated with 200 mg/l anastrozole via the drinking water for periods ranging from 2 weeks to 1 year. Plasma FSH and testosterone concentrations were increased significantly (P<0·001) during the first 19 weeks of treatment. However, LH concentrations were increased only at 19 weeks (P<0·001) in anastrozole-treated rats, and this coincided with a further increase in circulating and intratesticular testosterone concentrations (P<0·05). No consistent change in inhibin-B concentrations was observed during the study. Suppression of plasma oestradiol concentrations could not be demonstrated in anastrozole-treated animals, but oestradiol concentrations in testicular interstitial fluid were reduced by 18% (P<0·01). Mating was again inhibited by anastrozole treatment, but could be restored by s.c. injection of oestrogen, enabling demonstration that rats treated for 10 weeks or 9 months were still fertile. Testis weight was increased by 19% and 6% after treatment for 19 weeks and 1 year, respectively. Body weight was significantly decreased (P<0·01) by 19 weeks of anastrozole treatment; after 1 year the animals appeared to have less fat as indicated by a 27% decrease in the weight of the gonadal fat pad. The majority of anastrozole-treated animals had testes with normal spermatogenesis but, occasionally, seminiferous tubules showed abnormal loss of germ cells or contained only Sertoli cells. Ten percent of anastrozoletreated animals had testes that appeared to contain only Sertoli cells, and one rat had 'giant' testes in which the tubule lumens were severely dilated. Morphometric analysis of the normal testes at 19 weeks showed no difference in the number of Sertoli cells or germ cells, or the percentage volumes of the seminiferous epithelium, tubule lumens and interstitium between control and anastrozoletreated rats. On the basis of the present findings, oestrogen appears to be involved in the regulation of FSH secretion and testosterone production, and is also essential for normal mating behaviour in male rats. Furthermore, these data suggest that the br...

Multiple Structural and Functional Abnormalities in the P450 Aromatase Expressing Transgenic Male Mice Are Ameliorated by a P450 Aromatase Inhibitor

“…39 In addition, it has been reported that a chronic adminis- tration of a P450arom inhibitor, anastrozole, results in a significant increase in testis weight and circulating and intratesticular T concentration in rats. 40 Furthermore, a recent study suggested that administration of E2 within a dose typically found in females can induce the spermatogenesis in hpg male mice, and despite of the increase in testicular weight, circulating androgen concentrations were still undetectable. 41 However, the amount of E2 supporting normal testis function forms a narrow window, while animal models with mild overexpression of P450arom show testicular interstitial cell abnormalities and disrupted spermatogenesis.…”

Oestrogen-induced androgen insufficiency results in a reduction of proliferation and differentiation of spermatogonia in the zebrafish testis

“…Furthermore, oestrogenic feedback on the hypothalamus and pituitary controls the synthesis and release of gonadotropins in mammals, and hence the testicular synthesis of androgens ( Jong et al 1975, Lindzey et al 1998, Turner et al 2000. Leydig cells express ER (Zhou et al 2002), and direct oestrogenic inhibition of steroidogenesis has been reported as well (Bartke et al 1977).…”

Histopathologic Effects of Anastrozole an Aromatase Enzyme Inhibitor on Rat Testicles

“…Turner et al reported testicular volume increases after long term anastrozole treatment in rats. 23 But although it was not statistically significantly different, there was an increased number of atrophic changes in spermatogenetic activity from Group 2 to Group 4. And increased leydig cell hyperplasia towards Group 4 were detected compared to control group associated to atrophic changes.…”