Antifertility effects of gossypol in male hamsters*†*Presented at the Thirty-Eighth Annual Meeting of The American Fertility Society, March 20 to 24, 1982, Las Vegas, Nevada.†Supported in part by a subcontract (PARFR-310) under a Prime Contract from Aid International Development (AID) and a grant from the National Institutes of Health (HD-14091)

The reversible effects of gossypol toxicity on male pigeons' reproductive performance

Background and Aim

Gossypol, a cotton seed derivative, is well known for its reversible antifertility in male reproduction across species. Its antifertility and reversibility effects on male reproductive function vary among species in dose-and time-dependent manners. In this study, the antifertility potential of gossypol in pigeons was evaluated for the first time to determine whether it might be used as a dietary supplement for pigeon population control.

Materials and Methods

Male pigeons were assigned into three experimental groups: The gossypol-treated group (n = 12), the sham control group (n = 6), and the negative control group (n = 6). There were two experimental periods: A gossypol-feeding period of 28 days and a gossypol-free period of 28 days. During the gossypol-feeding period, birds in the gossypol-treated group were fed 4 mg of gossypol extract per day. Birds in the sham control group were fed 0.5 mL of mixed ethanol and sunflower oil, while those in the negative control group were fed 0.5 mL of phosphate buffer saline. After the gossypol-feeding phase was completed, all remaining pigeons in all groups continued to receive their regular diet for an additional 28 days (gossypol-free phase). The body weight and semen quality of the birds in the experimental groups were compared to evaluate gossypol's antifertility effect.

Results

In the gossypol-treated group as compared to the control groups, the percentages of sperm motility and viability were significantly lower at 21 days, and the percentage of normal sperm morphology was significantly lower at 28 days during the gossypol-feeding period. After gossypol withdrawal, these antifertility effects were resumed and reached a comparable semen quality to the control groups within 14 days.

Conclusion

Gossypol supplementation (4 mg/day for 28 days) could lower male pigeons' reproductive performance in terms of sperm motility, viability, and sperm morphology. Such infertility was, however, reversible within 14 days after gossypol withdrawal without any side effects on the pigeons, suggesting its application as a safe contraceptive feeding for male pigeons.

Reproductive toxicological effects of gossypol on male rabbits: semen characteristics and hormonal levels

The objective of this study was to evaluate the effects of two sublethal doses (4 and 20 mg/kg live weight (LW); every other day) of gossypol on semen and hormonal characteristics of male rabbits. The experiment lasted 16 weeks and included two periods: a treatment period (first 8 weeks) where the animals were given the test materials, and a recovery period (second 8 weeks) where drugs were withdrawn. Results showed that LW and respiration rate (RR) decreased ( P<0·05) among animals that received gossypol, while rectal temperature increased ( P<0·05). Animals in gossypol treatment groups had decreased ( P<0·05) blood plasma levels of tri-iodothyronine (T3) and testosterone. This was accompanied by reductions ( P<0·05) in sperm concentration, total sperm output, percentage incidence of forward motility, total functional sperm fraction and semen initial fructose concentration. Gossypol however increased ( P<0·05) reaction time (i.e. decreased libido), percentages of dead sperm and abnormal sperm (AbSp) and altered acrosomes. Estimated weights of testes and semen ejaculate volume increased ( P<0·05) possibly due to increased water retention. Values of LW, RR, AbSp, and blood plasma T3 and testosterone returned to control levels after withdrawal of gossypol, while the effect of this drug on other parameters continued during the recovery period.

Effect of textile waste water on the spermatogenesis of male albino rats

Textile waste water released from dyeing and printing industries situated in Sanganer, Jaipur (India), brought about inhibition of spermatogenesis in male rats. Water analysis showed the presence of heavy metals at more than permissible limits. Oral administration of waste water to the rats at the dose level of 26.6 ml kg(-1) body wt. significantly reduced the weights of testes, epididymides and seminal vesicle. Treated animals showed a notable depression of various stages of spermatogenesis. The production of spermatids was inhibited by 70.8% in waste-water-treated rats. The populations of spermatogonia, preleptotene spermatocytes and secondary spermatocytes were decreased by 67.2, 71.1 and 73.2%, respectively. The total number of Sertoli cells was affected after waste water treatment. Reduced sperm count and motility resulted in treated groups. A significant fall in the content of various biochemical parameters of reproductive tissues was observed after water treatment.

Effect of feeding gossypol in cottonseed meal on growth, semen quality, and spermatogenesis of yearling Holstein bulls

Yearling Holstein bulls were fed a corn silage ration supplemented with either cottonseed meal with gossypol or soybean meal in two trials to evaluate the effect of feeding gossypol on reproductive characteristics. In Trial 1, roughage to concentrate ratio was 88:12 and was fed for 60 d. In Trial 2, roughage to concentrate ratio was 50:50 and was fed for 42 d. Cottonseed meal concentrate had 3.03 g total gossypol/kg DM. Cottonseed meal concentrate was fed to provide 6 and 30 mg total gossypol/kg BW per d in Trials 1 and 2. Ejaculates were collected twice weekly via artificial vagina and critiqued for quantity and quality before and after thawing and after postthaw incubation. Leptotene spermatocytes to Sertoli cell ratio in stage 1 tubules was used to evaluate spermatogenesis. Growth characteristics and tissue total gossypol concentrations were also evaluated. No gossypol was found in plasma taken before, during, or after Trial 1 or from body organs or plasma taken during or after Trial 2. No signs of gossypol toxicity were observed, and growth characteristics were similar on both rations. Gossypol in cottonseed meal fed at low to moderate concentrations was not deleterious to seminal quantity or quality, and spermatogenesis was unaffected by treatment.

Interspecies comparison of pharmacokinetic profile and bioavailability of (+/-)-gossypol in male Fischer-344 rats and male B6C3F mice

Gossypol is a naturally occurring yellow substance in cotton plant that has male reproductive toxicity both in humans and some experimental animal species. Interspecies oral bioavailability and pharmacokinetic profile of (+/-)-gossypol were compared in male Fischer-344 rats and B6C3F mice after a 1) single intravenous dose, 2) single oral dose, and 3) 14 consecutive, daily, oral doses; all doses were 10 and 50 mg/kg rats and mice, respectively. In both species, the intravenous plasma (+/-)-gossypol concentrations showed a triexponential pattern, indicating a 3-compartment, open-model system. The apparent half-life of elimination of (+/-)-gossypol following intravenous injection was 9.1 h and 7.7 h in rats and mice, respectively. The total plasma clearance (Cl), volume of distribution (Vd), and AUCplasma after a single intravenous injection were 1.84 and 1.23 l/h per kg, 0.20 and 1.74 l/kg, and 36.0 and 115.8 mg.h/l, in rats and mice, respectively. The bioavailability of a single, oral dose of (+/-)-gossypol was 86% and 14.3% in rats and mice, respectively. In rats the change in plasma (+/-)-gossypol concentration after a single, dose was monophasic; multiple doses showed a biphasic pattern. In mice a single, dose of (+/-)-gossypol showed a biexponential plasma concentration pattern; daily dosing was monoexponential and was eliminated twice as fast as the single dose. Also, multiple doses of (+/-)-gossypol in the mouse were eliminated 7 times faster than in the rat. These findings are consistent with previous results that daily, oral dosing of (+/-)-gossypol, but not a single dose, produces infertility in the male rat, while the mouse is insensitive to (+/-)-gossypol action. The results of this study indicate that differential sensitivity of rats and mice to the contraceptive action of (+/-)-gossypol may be related, at least in part, to its pharmacokinetic profiles in both species.

Studies on mechanism(s) of antifertility action of gossypol in rat and hamster

This study was undertaken with a view to investigate the possible mechanism(s) of antifertility action of gossypol acetate in rats and hamsters. Adult male rats were treated by gavage with 30 mg/kg/day of gossypol for 7 weeks and adult male hamsters were treated similarly with 20 mg/kg/day gossypol for 8 weeks. The treatment caused a marked reduction in the weights of testis and epididymis. Histological examination of the testis in the two species revealed presence of seminiferous tubules showing varying degrees of damage along with a large number of normal tubules. Exfoliation of germ cells and spermatogenic arrest at spermatid stage was a common feature. Leydig cells presented normal morphological features. Though there was a reduction in the diameter of epididymal tubules, the epithelium did not show any morphological alterations. Examination of vasal flushings revealed marked reduction in sperm population and consisted of decapitated and immotile spermatozoa. Gossypol caused a significant reduction in the levels of total protein, RNA and DNA, and a marginal decrease in glycogen content in the testis. This was accompanied by a reduction in the activities of SDH and MDH. Except for LDH activity which showed a marked rise, there was no effect on glycolytic enzymes in the testis. The concentrations of glycerylphosphorylcholine and sialic acid were reduced in the cauda epididymis. The antifertility effects of gossypol appear to be due to its action both on testis as well as on epididymis.

Ultrastructure of the testis and epididymis of Japanese quail (Coturnix coturnix japonica) administered gossypol

When Japanese quail were given gossypol acetic acid intramuscularly at 25 mg/kg body weight per day for 9 days, testis/body weights were reduced to 63% of those of controls. Lumina of the seminiferous tubules became smaller but were packed with tails of spermatids. Mitochondria of spermatids changed in shape from elongated to round. After administration of gossypol for 21 days, testis/body weights were 14% of those of controls. Lumina of seminiferous tubules were completely collapsed, germinal epithelia became much thinner, and basal lamina of the germinal epithelium underwent extensive ruffling. Although primary spermatocytes were seen, neither spermatids nor sperm were present. The cytoplasm of germinal epithelial cells was packed with numerous lipid droplets. At Day 8 of withdrawal following 21 days of gossypol administration, testis/body weights were 23% of those of controls. Reduced numbers of lipid inclusions and partial recovery of spermatogenesis in the testis were observed. In the epididymal region, epithelial cells of the ductuli efferentes progressively accumulated lipid droplets, and luminal collapse was seen after 21 days of gossypol administration. After gossypol administration for 21 days, no sperm were found in the ductus epididymidis, the lumina were collapsed, and microvilli of the epithelial cells were lost. At Day 8 of withdrawal after 21 days of gossypol administration, lipid content was reduced in the ductuli efferentes. The lumina of the ductus epididymidis were open, but no spermatozoa were seen. These observations indicate that gossypol severely altered tissues of the quail testis and epididymal region. However, this alteration seems to be reversible.

A developmental toxicity evaluation of gossypol

In utero development was analyzed in pregnancies that resulted from matings between gossypol-treated male rats and untreated female rats, and in pregnancies in which gossypol was administered to the pregnant rat only. Gossypol treatment of males had no effect on the outcome of pregnancy. There was no significant effect on resorption, fetal growth, or malformation rate. Similarly, gossypol administered to pregnant dams at stages during organogenesis had no observable effect on pregnancy. Under the conditions of this experiment, gossypol administered to either the breeding male rat or the pregnant female rat had no demonstrable adverse effect on development in utero.

Inhibition of lactate dehydrogenase-X by imino-derivatives of gossypol:structure activity relationship

Six imino-derivatives (II, III, IV, V, VI, VII) of gossypol (I) have been synthesized, and their effects were evaluated on the purified mouse lactate dehydrogenase-X. Three of these derivatives (V, VI, VII) with aldehyde groups substituted with hydrophobic functionalities showed equivalent or more inhibitory effects on lactate dehydrogenase-X than gossypol, whereas three other derivatives (II, III, IV) with aldehyde groups substituted with hydrophilic functional groups lost the ability to inhibit lactate dehydrogenase-X. It is suggested that two aldehyde groups of gossypol are not essential to inhibit lactate dehydrogenase-X. Furthermore, the hydrophobic property of the gossypol molecule seems to play a more important role in inhibiting lactate dehydrogenase-X. Therefore, lactate dehydrogenase-X inhibition by gossypol may not be associated with its antifertility mechanism, because the aldehyde group of gossypol is known to be required for its antifertility effect.

Effects of gossypol on the estrous cycle and ovarian weight in the rat

The effect of subcutaneously injected gossypol on the estrous cycle and ovarian weights in rats was examined. Daily injections of 5 or 10 mg gossypol/kg/day for 20 days significantly reduced the ovarian weights by 32% and 29%, respectively. Injections of 0.1 and 1.0 mg gossypol/kg/day had no significant effect on ovarian weight. Similarly, ovarian weights were significantly reduced by 37% when hemi-ovariectomized animals were injected with 10 mg gossypol/kg/day for 15 days whereas those of control animals increased in weight by 15%. Animals receiving 5 or 10 mg gossypol/kg/day essentially remained in diestrus by the 15th or the 10th day of injections, respectively. No significant change was found in the liver, adrenal gland or body weight of gossypol-treated rats.

The embryotoxicity of gossypol

In utero development was analyzed in pregnancies that resulted from matings between gossypol-treated male rats and untreated female rats and in pregnancies in which gossypol was administered to the pregnant rat only. Gossypol treatment of males had no effect on the outcome of pregnancy. There was no significant effect on resorption, fetal growth, or malformation rate. Similarly, gossypol administered to pregnant dams at stages during organogenesis had no observable effect on pregnancy. Under the conditions of this experiment, gossypol administered to either the breeding male rat or the pregnant female rat had no demonstrable adverse effect on development in utero.

Effect of gossypol acetate on guinea pig epididymal spermatozoa in vivo and their susceptibility to capacitation in vitro

To determine the effects of gossypol acetate on guinea pig epididymal and vas deferens sperm maturity and in vivo susceptibility to in vitro capacitation and the acrosome reaction, we examined spermatozoa removed from 37 animals fed gossypol acetate (10-15 mg/kg/day) for 5 to 9 weeks, and 15 vegetable oil-fed, age-paired control animals. In gossypol-treated, reproductively immature guinea pigs, the number of spermatozoa in the epididymis was markedly reduced (P less than 0.01) compared to controls, whereas the presence of spermatids and spermatocytes increased in the epididymis with the duration of gossypol administration. In sexually mature guinea pigs (given 15 mg/kg/day for 5 weeks), the epididymal sperm survival and forward motility were decreased significantly (P less than 0.025 and P less than 0.01, respectively), although the density of mature spermatozoa was the same as in control animals. The percentage of induced acrosome reactions (26.4 +/- 12%) was almost three-fold lower than that of control animals (72.8 +/- 4.6%). Also, in 31.5 +/- 3.8% of spermatozoa from gossypol-treated animals, as compared to only 2.4 +/- 0.7% of controls, the cytoplasmic droplet failed to migrate to its proper position in the midpiece and was retained in the neck region. With a few exceptions, spermatozoa from both experimental and control groups had comparable patterns of freeze-fractured membrane differentiations. Susceptibility to the induced acrosome reactions and the position of the retained cytoplasmic droplet reversed within 3 weeks after the end of gossypol feeding. This study helps establish the suitability of the guinea pig for studies on gossypol-induced infertility.

Toxic effects of the antifertility agent gossypol in male rats

In the present investigation the influence of gossypol on the male sex function and toxicology in the rat have been studied. Gossypol was injected daily for 5 weeks to adult male rats of the Sprague-Dawley strain with 1 or 10 mg/kg body wt. The low dose of gossypol (1 mg/kg body wt.) did not have any effect on the following parameters: plasma testosterone concentrations, body growth, kidney weights, sex organ weights (ventral prostate, seminal vesicle, epididymis), testicular weights, blood flow to testes, epididymides and ventral prostate as measured with the microsphere technique, intraarterial blood pressure and morphology of testis and epididymis. The plasma testosterone response to acute LH-injection was not significantly different in gossypol-treated rats when compared to control rats. The high dose of gossypol (10 mg/kg body wt) caused signs of tubular degeneration, retarded body growth, markedly reduced testosterone concentrations, involutions of the ventral prostate and seminal vesicles and gastrointestinal disturbances. After 5 weeks of treatment the mortality rate was 13%. It is concluded that gossypol is a very toxic substance in rats, since only a 10-fold increase of a non-effective dose caused serious side effects in addition to its antifertility effects.

Inhibition by gossypol of oxidoreductases from Trypanosoma cruzi

The effects of gossypol, a polyphenolic compound isolated from the cotton plant upon six oxidoreductases from cultured epimastigotes of Typanosoma cruzi were studied. Gossypol was a powerful inhibitor of the alpha-hydroxyacid and malate dehydrogenases, NAD-linked enzymes, and of glutamate dehydrogenase, malic enzyme and glucose-6-phosphate dehydrogenase, NADP-dependent enzymes. The drug did not have an effect on succinate dehydrogenase, a flavoprotein. The Ki values with respect to substrate were 0.73, 0.3 and 3.5 microM for alpha-hydroxyacid, malate and glutamate dehydrogenases, respectively, and 1.1, 0.19 and 7.8 microM with respect to the coenzyme. Inhibition was noncompetitive with respect to substrate and uncompetitive in relation to the coenzyme.