Antifertility efficacy of gossypol acetic acid in male rats

The endocrine status of gossypol - treated male rats

Male adult Wistar rats were exposed daily or every other day to oral gossypol acetic acid (GAA) concentrations of 2.5-30 mg/kg for 10-20 weeks. Controls received the GAA-suspension medium or were left completely untreated. The serum concentrations of testosterone, LH and FSH as well as the weight of testis, epididymis, prostate, seminal vesicle, coagulating gland, and pituitary were determined. The accessory sex organs were prepared for light microscopy. Significant antifertility effect in these animals was achieved at GAA-dosage of 15 mg/kg and higher. GAA-administration neither altered the serum hormonal profiles nor the reproductive organ weights in comparison to the controls. Accordingly, light microscopical examination revealed no alterations in the histological picture of prostate, seminal vesicle and coagulating gland when compared with the controls. The results indicate that GAA does not interfere with the hypothalamic-pituitary-gonadal axis in male adult rats.

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8 weeks) where the animals were given the test materials, and a recovery period (second 8 weeks) where drugs were withdrawn.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.

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.

Subchronic oral administration of gossypol-acetic acid (GAA) alters the distribution and utilization of radioiron in male rats

Gossypol-acetic acid (GAA) has been shown to be a powerful chelator of iron. To determine how subchronic administration of GAA affects the distribution and utilization of radioiron, male Holtzman rats, which had received a daily oral dose of GAA (20 mg/kg body weight) for 16 weeks, were injected i.p. with [59Fe]citrate (activity = 16.5 muCi/kg body weight) and [59Fe] incorporation into circulating erythrocytes, bone marrow, liver, spleen, skeletal muscle, and urine was measured 6, 12, or 24 h after [59Fe] administration. Iron [59Fe] incorporation was enhanced in the spleens, livers, bone marrow, and blood of the GAA-treated rats, and increased as the time post-[59Fe] injection increased. Hematological parameters remained within normal limits throughout the 16-week treatment period, suggesting an erythropoietic compensation in the GAA-treated rats. Iron status was markedly different in the GAA-treated rats at the end of the 16 week treatment period, suggesting altered iron utilization. The data suggest that [59Fe] is preferentially distributed to the erythroid tissues of GAA-treated rats for utilization in erythropoiesis.

Clinical microdose study of gossypol: effect on sperm motility and renal function

This study is part of a series designed to identify the smallest effective gossypol dose for male fertility control. Three men, aged 31-35 years, were administered gossypol, 10 mg/day, orally for 3 months. Urinalysis and assays for plasma hormone values, including cortisol, beta 2-microglobulin, potassium, and BUN, showed no changes during treatment. Forward sperm motility, however, was severely affected by the end of the treatment period (less than 4% forward motility). Sperm density also showed a marked decrease. The subjects developed no undue side effects.

Effects of gossypol on human and monkey sperm motility in vitro

The effects of gossypol acetic acid on human and monkey sperm motility in vitro were studied by using multiexposure photography technique. Human and monkey spermatozoa were inhibited by gossypol to different degrees. Monkey sperm were absolutely immotile within 15 min after 50 microM of gossypol was added, but motility of human spermatozoa was not completely suppressed by gossypol even at the highest concentration used and longest duration of exposure.

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.

In vivo study of LDH isoenzyme activities in heart, liver and testis cytosols of gossypol-treated rats

LDH isoenzyme activities of heart, liver and testis homogenates were measured in rats treated for 15 or 30 days with 30 mg gossypol acetic acid/kg body weight daily, a dose which severely suppressed sperm motility. No differences in LDH activities of the examined organs were found in comparison with control animals. LDH-X, the main LDH isoenzyme in spermatozoa and testicular germ cells from primary spermatocytes onwards was also unaffected. These results contrast with in vitro experiments on human, rabbit, and boar spermatozoa, purified bovine LDH-X and rat testis homogenate which show dose-dependent inhibition of LDH-X after incubation with gossypol. Our results therefore suggest that inhibition of LDH by gossypol is not the primary cause of sperm immotility.

Semen characteristics of gossypol-treated langurs (Presbytis entellus entellus Dufresne)

Gossypol isolated from cottonseed was fed to sexually adult male langurs at 50 and 100 mg/kg body weight per day for 90 days. Semen was collected every 2 wk, and the observations made on semen characteristics showed gossypol's detrimental effect. The gossypol administration caused a significant decline in percent sperm cells motility and a significant rise in abnormalities. The semen characteristics returned to normal levels during a 180-day recovery period following the discontinuation of gossypol treatment. A clear relationship exists between the inhibition of sperm cell motility and dose as well as duration of gossypol treatment. The testicular biopsies taken from two langurs after 90 days of gossypol treatment showed normal histoarchitecture at both the dose levels.

Effect of gossypol on testicular testosterone production in vitro

Testicular minces were utilized to study the effect of gossypol on testosterone production. Testosterone production was assessed in both control nd gossypol treated groups after 0 to 4 hours incubation in the presence of hCG. Media testosterone was measured by radioimmunoassay. Gossypol did not alter testosterone production when present in incubates at the concentrations of 3.5 x 10(-5) M, 7 x 10(-5) M and 3.5 x 10(-4) M. Preincubation of testis mince with gossypol (7 x 10(-6) M, 7 x 10(-5) M, 3.5 x 10(-4) M) for 1 to 4 hours did not alter subsequent hCG induced testosterone production in mature rats. Testosterone production however, was inhibited in immature rat testis when the whole testis was incubated for 4 hours with different concentrations of gossypol (7 x 10(-6) M, 7 x 10(-5) M, 3.5 x 10(-4) M). In vivo testosterone production was not inhibited in the immature rat testis 24 hours after oral administration of gossypol (100 mg/kg).

Toxicity of gossypol at antifertility dosages in male rats: statistical analysis of lethal rates and body weight responses

The lethal rates and body weight responses of male Wistar rats following oral treatment with gossypol acetic acid (GAA) at dosages of 2.5-30 mg/kg were analysed by various statistical procedures. Daily treatment with GAA for 10 weeks was associated with lethal rates significantly different from placebo groups in both the low dose (2.5, 5.0, and 7.5 mg/kg, p less than 0.05) and high dose groups (15, 20 and 30 mg/kg, p less than 0.01). The pronounced mean body weight gain observed in placebo groups, was suppressed in the GAA-treated groups at each dose level after 10 weeks. This indicates decreased appetite and/or lessened feed utilisation caused by GAA activity. GAA administration at a dose of 30 mg/kg every other day exerted identical deleterious effects as daily treatment. As derived from the antifertility responses of the GAA treatment groups it was evident that the toxic activity of GAA was not related to its antifertility efficacy. It is concluded that GAA has remarkable toxicity at antifertility dosages in rats.