Collaborative work to determine the optimal administration period and parameters to detect drug effects on male rat fertility--study on estradiol benzoate effects

Daily GnRH agonist treatment delays the development of reproductive physiology and behavior in male rats

The present study was designed to examine the effects of suppressing pubertal onset with leuprolide acetate, a gonadotropin releasing hormone (GnRH) agonist. Starting on postnatal day (PD) 25, male Long-Evans rats were injected daily with either leuprolide acetate (25 μg/kg dissolved in 0.9% sterile physiological saline; n = 13) or sterile physiological saline (1.0 ml/kg 0.9% NaCl; n = 14) for a total of 25 days. Males were monitored daily for signs of puberty (i.e., preputial separation). On the last day of leuprolide treatment (PD 50), half of each treatment group was injected with 10.0 μg of estradiol benzoate (EB) daily for three consecutive days (PD 50-52) and 1.0 mg of progesterone (P) on the 4th day (PD 53), whereas the other half of each treatment group received oil injections. Four hours after P injections, all subjects were given the opportunity to interact with a gonadally-intact male and a sexually receptive female rat (i.e., a partner-preference test with and without physical contact). Copulatory behavior and sexual motivation were measured. Hormone injections and mating tests were repeated weekly for a total of 3 consecutive weeks. Results showed that leuprolide delayed puberty as well as the development of copulatory behavior and the expression of sexual motivation. By the last test, the leuprolide-treated subjects showed signs of catching up, however, many continued to be delayed. Estradiol and progesterone mildly feminized male physiology (e.g., decreased testes weight and serum testosterone) and behavior (e.g., increased lordosis), but did not interact with leuprolide treatment.

Comparison of the effects of mesquite pod and Leucaena extracts with phytoestrogens on the reproductive physiology and sexual behavior in the male rat

Mesquite (Prosopis sp.) and Leucaena leucocephala are widespread legumes, widely used to feed several livestock species and as food source for human populations in several countries. Both mesquite and Leucaena contain several phytoestrogens which might have potential estrogenic effects. Thus, the aim of this study was to evaluate the effects of mesquite pod and Leucaena extracts on several aspects of behavior and reproductive physiology of the male rat. The effects of the extracts were compared with those of estradiol (E2) and of two isoflavones: daidzein (DAI) and genistein (GEN). The following treatments were given to groups of intact male rats: vehicle; mesquite pod extract; Leucaena extract; E2; DAI; GEN. The results indicate that mesquite pod and Leucaena extracts disrupt male sexual behavior in a similar way to DAI and GEN, but less than E2. The main disruptor of sexual behavior was E2, however after 40 and 50days of administration, both extracts and phytoestrogens disrupted sexual behavior in a similar way to E2. The extracts also increased testicular germ cell apoptosis, decreased sperm quality, testicular weight, and testosterone levels, as phytoestrogens did, although these effects were less than those caused by estradiol. The number of seminiferous tubules with TUNEL-positive germ cells increased in extracts treated groups in a similar way to phytoestrogens groups, and E2 caused the greatest effect. The number of TUNEL-positive cells per tubule increased only in Leucaena extract and E2 groups, but not in mesquite- and phytoestrogens-treated groups. Spermatocytes and round spermatids were the TUNEL-positive cells observed in all experimental groups. This effect was associated with smaller testicular weights without atrophy in experimental groups compared with control. Testicular atrophy was only observed in estradiol-treated males. Testosterone decreased in males of all experimental groups, compared with control, this androgen was undetectable in E2 treated males. These results suggest that mesquite pod and Leucaena extracts cause effects similar to those of phytoestrogens in male rat reproduction, these effects were lower than those caused by E2.

Effects of Tripterygium wilfordii multiglycosides on sex hormones and receptors in mandarin vole Leydig cells

Multiglycosides ofTripterygium wilfordii(GTW) have been found to exhibit reversible antifertility effects through complex mechanisms. The positive expression of sex hormones and receptors in Leydig cells were investigated following GTW treatment to determine the impact of GTW on male mandarin vole (Microtus mandarinus) fertility. Compared to the control group, body weight, testis and epididymis weight were not affected by GTW, but the number of sperm sharply declined. There were significant decreases in the thickness of seminifeous epithelium and epididymal epithelium, and the diameter of seminiferous tubules. The expression of estrogen receptor alpha (ERα) in Leydig cells significantly decreased and estradiol (E) expression significantly increased. Testosterone (T) and androgen receptor (AR) expression were not affected. These results show that GTW may impair fertility in male mandarin voles via interference with spermatogenesis. This may be associated with an alteration in estrogen activation rather than suppression of T and AR in Leydig cells and suggests the estrogen system of Leydig cells is of major importance for the GTW’s antifertility effects.

beta-estradiol 3-benzoate affects spermatogenesis in the adult mouse

beta-estradiol 3-benzoate (E(2)B) (10, 16, 20, 40, 80 and 160 microg/kg body weight) was administered daily to experimental groups of adult mice for the following periods; 2, 3 days, 1, 2, 4, and 8 weeks. Morphological changes in the testes were observed by both light and electron microscopy. Exfoliation of the germ cells was observed in the lumen of the seminiferous tubule. The spermatogenic cycle, especially stage XII, was disordered. Spermatids older than step 6 were severely affected. Detected abnormalities in the spermatids were deformation of the nucleus and acrosome. Partial deletion in the Sertoli-spermatid ectoplasmic specialization was also observed. Germ cells younger than step 7 spermatids were not affected morphologically. These abnormalities were not detected in the mice treated with the chemical at less than 16 microg/kg body weight. It is concluded that the chemical seems to affect round spermatids metabolically, but the morphological effect can be detected only from the spermatids older than step 6. The effects of the chemical on adult mice were reversible.

Epididymal sperm motion as a parameter of male reproductive toxicity: sperm motion, fertility, and histopathology in ethinylestradiol-treated rats

The present study was designed to characterize the effect of ethinylestradiol (EE) on epididymal sperm motion using a computer-assisted sperm analysis system (CASA), and to elucidate the correlation between sperm motion endpoints and other measures including fertility, histopathologic, and endocrinologic endpoints. EE was orally given to adult male rats at a daily dosage of 10 mg/kg for 3 and 5 d, and at daily dosages of I and 10 mg/kg for 1, 2, 3, and 4 weeks. Changes in sperm motion were first detected after one week of treatment. Of nine sperm motion parameters, the percentage of motile sperm, velocity, and amplitude of the lateral head displacement (ALH) were decreased in the 10 mg/kg dosing group. Accompanying the decreases in those parameters, the male fertility indices in the 10 mg/kg dosing group were reduced after one week of treatment, and no males in this group could impregnate intact females after 2 weeks or more of treatment. The number of sperm heads in the cauda epididymis in the 10 mg/kg dosing group was reduced to about one-half that in the control group after one week of treatment, whereas the total number of homogenization-resistant advanced spermatids in the testis was not altered and only a slight change was detected in the number and morphology of germ cells in the testis. These results suggest that reduction in the number of epididymal sperm and in sperm motion are not secondary to testicular alteration. However, after 3 weeks of treatment, the number of sperm heads in the testis was drastically reduced with severe atrophy of the seminiferous tubules both in the 1 and 10 mg/kg dosing groups. The profiling of epididymal luminal fluid proteins indicated that two major bands that migrated with molecular weights of about 22 and 23 kDa were weakened and their density was reduced to approximately 70% of the control after 5-d and one week treatments in the 10 mg/kg dosing group. Circulating testosterone declined drastically after 3 d of treatment and remained at undetectable levels with a concomitant decline of circulating LH and FSH, suggesting that EE inhibits testosterone secretion immediately via a negative feedback system, and there follow changes in the accessory reproductive organs including the epididymis. These results indicate that EE affects epididymal spermatozoa before testicular germ cells via a testosterone deficiency, when it is administered at extremely high dosages. The reduction in the sperm motion manifested as decreases in the percentage of motile sperm, ALH, and velocity, is considered to be responsible for the onset of infertility. Sperm motion analysis could be particularly useful for detecting the toxic effects of chemicals that act through the endocrinologic system on the epididymis.