Mechanisms involved in reproductive damage caused by gossypol in rats and protective effects of vitamin E

BACKGROUND: Gossypol is a chemical present in the seeds of cotton plants (Gossypium sp.) that reduces fertility in farm animals. Vitamin E is an antioxidant and may help to protect cells and tissues against the deleterious effects of free radicals. The aim of this study was to evaluate the mechanisms of reproductive toxicity of gossypol in rats and the protective effects of vitamin E. Forty Wistar rats were used, divided into four experimental groups (n = 10): DMSO/ saline + corn oil; DMSO/saline + vitamin E; gossypol + corn oil; and gossypol + vitamin E. RESULTS: Fertility was significantly reduced in male rats treated with gossypol in that a significant decrease in epididy-mal sperm count was observed (P < 0.05) and the number of offspring was significantly reduced in females mated with them (P < 0.05). This dysfunction was prevented by vitamin E. Gossypol caused a significant increase in the activity of the enzymes glutathione peroxidase (P < 0.01) and glutathione reductase (P < 0.01), but vitamin E did not reduce the enzyme activities (P > 0.05). The levels of reduced glutathione and pyridine nucleotides in testis homogen-ate were significantly reduced by gossypol (P < 0.05 and P < 0.01, respectively) and this reduction was accompanied by increased levels of oxidized glutathione (P < 0.05). Vitamin E showed a preventive effect on the changes in the levels of these substances. Gossypol significantly increased the levels of malondialdehyde (P < 0.01), a lipid peroxida-tion indicator, whereas treatment with vitamin E inhibited the action of the gossypol. Vitamin E prevented a decrease in mitochondrial ATP induced by gossypol (P < 0.05). CONCLUSIONS: This study suggests that the reproductive dysfunction caused by gossypol may be related to oxidative stress and mitochondrial bioenergetic damage and that treatment with vitamin E can prevent the infertility caused by the toxin.

Morfologia testicular e qualidade espermática de touros da raça Nelore, submetidos à dieta contendo gossipol / Testes morphology and sperm quality of Nelore bulls fed a gossypol-enriched diet

Com o objetivo estudar o efeito de dieta contendo gossipol sobre a qualidade seminal e morfologia dos testículos de touros da raça Nelore, utilizaram-se 16 animais, distribuídos em dois tratamentos: T1, oito touros submetidos a dieta contendo 20 por cento de caroço de algodão e T2, oito touros submetidos a dieta isenta de gossipol. Realizaram-se coletas de sêmen para avaliar a qualidade seminal. Os testículos dos animais foram retirados ao final dos 73 dias de experimento, fragmentos dos mesmos foram preparados para serem analisados em microscopia eletrônica de transmissão e outros fixados em lâminas e corados por hematoxilina-eosina. O consumo médio de caroço de algodão/animal/dia de 1,71kg interferiu na morfologia dos testículos; os túbulos seminíferos apresentaram menor espessura de parede, redução no número de camadas de células espermatogênicas e no volume dos núcleos da célula de Sertoli em relação aos do T2. Por microscopia eletrônica observouse que os touros do T1 apresentavam células de Sertoli com membrana citoplasmática enrugada, acúmulo de lipídeos no citoplasma, mitocôndrias deformadas e algumas espermátides estavam em apoptose. Touros do T1 apresentaram redução na motilidade espermática, aumento no percentual de defeitos espermáticos maiores e totais em relação aos animais do T2. O gossipol alterou a morfologia testicular e reduziu a qualidade espermática dos touros...

We studied the effect of a gossypol-enriched diet on the quality of semen and the morphology of testes of Nelore bulls. Sixteen animals were scheduled for 2 treatments: T1, 8 bulls fed a diet containing 20 percent cottonseed and T2, 8 bulls fed a gossypol-free diet. Semen samples were collected in order to evaluate the semen quality. At the end of the 73-day period of treatment, the testes were removed and tissue fragments were prepared for transmission electron microscopy or fixed on slides and stained with haematoxylin-eosin for light microscopy. The mean daily intake of cottonseed by T1 bulls was 1.71 kg/animal, which interfered on testes morphology; the seminiferous tubules had less thick walls, fewer layers of the spermatogenic lineage cells and reduced volumes of Sertoli cell nuclei with regard to T2 bulls. Electron microscopy analyses revealed that the Sertoli cells from T1 animals had a rough cytoplasmic membrane, lipid accumulation in the cytoplasm, deformed mitochondriae; in addition, some apoptotic spermatids were seen. T1 bulls showed reduction of sperm motility and an increase of the percentage of major and total sperm defects in relation to the animals of T2 group. It is concluded that a gossypol-enriched diet promoted alterations in the testicles morphology and it reduced the sperm quality of bulls...

Morfologia testicular e qualidade espermática de touros da raça Nelore, submetidos à dieta contendo gossipol / Testes morphology and sperm quality of Nelore bulls fed a gossypol-enriched diet

Com o objetivo estudar o efeito de dieta contendo gossipol sobre a qualidade seminal e morfologia dos testículos de touros da raça Nelore, utilizaram-se 16 animais, distribuídos em dois tratamentos: T1, oito touros submetidos a dieta contendo 20 por cento de caroço de algodão e T2, oito touros submetidos a dieta isenta de gossipol. Realizaram-se coletas de sêmen para avaliar a qualidade seminal. Os testículos dos animais foram retirados ao final dos 73 dias de experimento, fragmentos dos mesmos foram preparados para serem analisados em microscopia eletrônica de transmissão e outros fixados em lâminas e corados por hematoxilina-eosina. O consumo médio de caroço de algodão/animal/dia de 1,71kg interferiu na morfologia dos testículos; os túbulos seminíferos apresentaram menor espessura de parede, redução no número de camadas de células espermatogênicas e no volume dos núcleos da célula de Sertoli em relação aos do T2. Por microscopia eletrônica observouse que os touros do T1 apresentavam células de Sertoli com membrana citoplasmática enrugada, acúmulo de lipídeos no citoplasma, mitocôndrias deformadas e algumas espermátides estavam em apoptose. Touros do T1 apresentaram redução na motilidade espermática, aumento no percentual de defeitos espermáticos maiores e totais em relação aos animais do T2. O gossipol alterou a morfologia testicular e reduziu a qualidade espermática dos touros [...]

We studied the effect of a gossypol-enriched diet on the quality of semen and the morphology of testes of Nelore bulls. Sixteen animals were scheduled for 2 treatments: T1, 8 bulls fed a diet containing 20 percent cottonseed and T2, 8 bulls fed a gossypol-free diet. Semen samples were collected in order to evaluate the semen quality. At the end of the 73-day period of treatment, the testes were removed and tissue fragments were prepared for transmission electron microscopy or fixed on slides and stained with haematoxylin-eosin for light microscopy. The mean daily intake of cottonseed by T1 bulls was 1.71 kg/animal, which interfered on testes morphology; the seminiferous tubules had less thick walls, fewer layers of the spermatogenic lineage cells and reduced volumes of Sertoli cell nuclei with regard to T2 bulls. Electron microscopy analyses revealed that the Sertoli cells from T1 animals had a rough cytoplasmic membrane, lipid accumulation in the cytoplasm, deformed mitochondriae; in addition, some apoptotic spermatids were seen. T1 bulls showed reduction of sperm motility and an increase of the percentage of major and total sperm defects in relation to the animals of T2 group. It is concluded that a gossypol-enriched diet promoted alterations in the testicles morphology and it reduced the sperm quality of bulls [...]

Male contraception: expanding reproductive choice.

The development of steroid-based oral contraceptives had revolutionized the availability of contraceptive choice for women. In order to expand the contraceptive options for couples by developing an acceptable, safe and effective male contraceptive, scientists have been experimenting with various steroidal/non-steroidal regimens to suppress testicular sperm production. The non-availability of a long-acting androgen was a limiting factor in the development of a male contraceptive regimen since all currently tested anti-spermatogenic agents also concurrently decrease circulating testosterone levels. A combination regimen of long-acting progestogen and androgen would have advantage over an androgen-alone modality since the dose of androgen required would be much smaller in the combination regimen, thereby decreasing the adverse effects of high steroid load. The progestogen in the combination regimen would act as the primary anti-spermatogenic agent. Currently, a number of combination regimens using progestogen or GnRH analogues combined with androgen are undergoing trials. The side effects of long-term use of androgens and progestogens have also undergone evaluation in primate models and the results of these studies need to be kept in view, while considering steroidal regimens for contraceptive use in men. Efforts are also being made to popularize non-scalpel vasectomy and to develop condoms of greater acceptability. The development of contraceptive vaccines for men, using sperm surface epitopes not expressed in female reproductive tract as source, still requires considerable research efforts.

Perspectives of contraceptive choices for men.

Apart from condoms and vasectomy, which have several limitations of their own, no other methods of contraception are available to men. Various chemical, hormonal, vas based and herbal contraceptives have been examined and few of them have reached the stage of clinical testing. Promising leads have been obtained from testosterone buciclate/undecanoate, alone or in combination with levonorgestrel butanoate or cyproterone acetate, RISUG, an injectable intravasal contraceptive and a few herbal products, particularly the seed products of Carica papaya. It is feasible that an ideal male contraceptive, that meets out all the essential criteria will be made available to the community in the near future.

Endocrine approach to male fertility control by steroid hormone combination in rat Rattus norvegicus L.

Effects of a combination of medoxy-progesterone acetate (MPA) and dihydrotestosterone (DHT) at a dose of 10 mg + 2 mg/kg, injected, in weekly to rats of proven fertility were investigated with respect to their fertility, sperm and organ functions. This hormonal regimen had no effect in body and organ weights except in the testis. A depletion in sperm reserves in testis and epididymis was noted in addition to a loss of their motility in the later. Alterations in cauda epididymal sperm viability and morphology and reduced levels of superoxide dismutase indicated changes in their plasma membrane permeability. Sperm acrosomal enzymes such as acrosin and hyaluronidase were also affected leading to a loss of their function. Consequently the fertility potential of these rats also impaired after 60 days of hormonal regimen. Testicular biochemical machinery revealed its altered metabolism and regressed spermatogenic activity accounting for its loss of weight. Similarly epididymal physiology also exhibited changes leading to impaired sperm maturation. However, toxicity studies showed no significant variations in liver and blood biochemical profiles indicating non-toxic nature of this combination. All these effects seemed to be transient and reversible upon withdrawal of treatment for 60 and 90 days gradually. Thus, this combination with aromatizable androgen is useful for induction of functional sterility.

Effect of fertility regulating agents on motility and zona-free hamster egg penetration by spermatozoa of bonnet monkey.

Administration of STS-557 (17 alpha-cyanomethyl-17 beta-hydroxyestra 4,9(10)-dien-3-one; 12 mg/monkey daily) for 4 weeks either alone or in combination with 20 Aet-1 (testosterone-trans-4-n-butyl cyclohexyl carboxylate; code CDB 1781; 40 mg/monkey single administration) had no significant effect on motility and zona free hamster egg penetration by spermatozoa of bonnet monkey, but continuation of the treatment for 12 weeks reduced (in one monkey treated with STS-557) or abolished (one treated with STS-557 and two with STS-557 + 20 Aet-1) the motility as well as zona-free hamster egg penetration (by spermatozoa of all treated monkeys). Motility and the ability to penetrate zona-free hamster egg returned to normalcy after 10 weeks of withdrawal of treatments. Active immunization of monkeys with ovine FSH (4 weeks after booster) had no adverse effect on motility of spermatozoa but none of the zona-free hamster eggs was fertilized. The correlation between motility and the capacity to penetrate the zona-free hamster eggs by monkey spermatozoa varies with the treatment. Such correlation was apparent in monkeys treated with STS-557 but not in monkeys immunized with ovine FSH.

Effect of depot medroxyprogesterone acetate on testis of albino rats: ultrastructural and biochemical studies.

Testis of male albino rats treated with depot medroxyprogesterone acetate DMPA, at the dose of 1 mg/animal/day for 60 days showed degenerative changes in the late spermatids. The changes were related with the mitochondrial sheath of the midpiece, including the plasma membrane enclosing the mitochondria and the mitochondrial cristae. Except lactate dehydrogenase and alkaline phosphatase, all the testicular marker enzymes, viz. beta-glucuronidase, hyaluronidase, sorbitol dehydrogenase and acid phosphatase registered a significant decrease. The ultrastructural and biochemical changes are correlated, as the cellular degeneration is responsible for decrease in the activity of the marker enzymes.

Antifertility effects of leaf extracts of some plants in male rats.

Ethanolic leaf extracts of different local folklore plants (Azadirachta indica, Beaumontia grandiflora, Chordia dichotoma, Casiarea tomentosa, Diospyros embryopteris, Milletia auriculata and Melia azedarach) were investigated for antifertility effects on male rats in oral doses of 100 mg/kg daily for 21 days. Though, none of these extracts interfered with spermatogenesis, anti-implantational and abortifacient effects were observed in females mated by the males fed with leaf extracts of A. indica and C. dichotoma. Leaf extract of B. grandiflora besides having anti-implantational and abortifacient effects, had luteolytic effects. Abolition of libido in 100% males by leaf extracts of D. embryopteris and M. azedarach and in 60% of males by extract of C. tomentosa preclude these plants for antifertility use.

Effect of a single maximal and low multiple doses of testosterone propionate (TP) on male reproductive organs in Long Evans rats.

Testosterone as a male contraceptive agent was tried on two age groups of rats of Long-Evans strain and with two dosage schedule. A general increase in accessory organs weights like seminal vesicle and ventral prostate was observed in all groups of animals with all dosage schedule. The testicular weight was reduced particularly in low multiple dosage group. Gross atrophy with marked irregularity in germ cell pattern and population, suppression of spermatogenesis and atrophy of Leydig cells in the testis of low multiple dosage group were evident without affecting the potentiality to sex drive. A further study is suggested to examine the time period needed for testicular recovery and return of normal spermatogenesis before its possible trial on male volunteers in Bangladesh.