Effects of Gossypol on the fertility of male rats, hamsters and rabbits

The potential roles of gossypol as anticancer agent: advances and future directions

Gossypol, a polyphenolic aldehyde derived from cottonseed plants, has seen a transformation in its pharmaceutical application from a male contraceptive to a candidate for cancer therapy. This shift is supported by its recognized antitumor properties, which have prompted its investigation in the treatment of various cancers and related inflammatory conditions. This review synthesizes the current understanding of gossypol as an anticancer agent, focusing on its pharmacological mechanisms, strategies to enhance its clinical efficacy, and the status of ongoing clinical evaluations.The methodological approach to this review involved a systematic search across several scientific databases including the National Center for Biotechnology Information (NCBI), PubMed/MedLine, Google Scholar, Scopus, and TRIP. Studies were meticulously chosen to cover various aspects of gossypol, from its chemical structure and natural sources to its pharmacokinetics and confirmed anticancer efficacy. Specific MeSH terms and keywords related to gossypol's antineoplastic applications guided the search strategy.Results from selected pharmacological studies indicate that gossypol inhibits the Bcl-2 family of anti-apoptotic proteins, promoting apoptosis in tumor cells. Clinical trials, particularly phase I and II, reveal gossypol's promise as an anticancer agent, demonstrating efficacy and manageable toxicity profiles. The review identifies the development of gossypol derivatives and novel carriers as avenues to enhance therapeutic outcomes and mitigate adverse effects.Conclusively, gossypol represents a promising anticancer agent with considerable therapeutic potential. However, further research is needed to refine gossypol-based therapies, explore combination treatments, and verify their effectiveness across cancer types. The ongoing clinical trials continue to support its potential, suggesting a future where gossypol could play a significant role in cancer treatment protocols.

Effects of diets containing gossypol on ovarian histology, function and fertility in prepubertal beef heifers

Forty-five crossbred beef heifers (weight = 268.3 +/- 5.7 kg) were used to determine the effects of dietary gossypol on ovarian morphology, erythrocyte fragility and fertility. Heifers were randomly assigned to 1 of 3 isonitrogenous dietary treatments. The diet consisted of rice mill feed and milo supplemented with soybean meal (n = 13; control), cottonseed meal (n = 16; low supplementation) which supplied 6.1 g free gossypol animal(-1) day(-1), or whole cottonseed (n = 16; high supplementation) which supplied 13.7 g free gossypol animal(-1) day(-1). The heifers were group-fed each diet for 64 days and were maintained on similar but separate fescue pastures overseeded with wheat. After 64 days, 4 heifers from each diet were confined and fed their respective diets. On Day 10 following estrus, each animal was unilaterally ovariectomized, and the ovary containing the corpus luteum was removed. The remaining ovary was removed 6 to 12 hours after detection of estrus in the next cycle. Erythrocyte fragility increased (P < 0.02) in heifers receiving gossypol compared with that of the controls. Cyclicity in the heifers was 81.3, 68.8 and 38.4% for high, low and control diets, respectively, at the end of the 64-day treatment period. First service conception rate, as determined by palpation per rectum, was similar among treatments (58.3, 33.3, 33.3% for high, low and control groups, respectively). Weight gain increased (P < 0.03) in control heifers compared with that of heifers receiving gossypol. Gross ovarian morphology and histology were similar for all heifers. Although gossypol produced mild toxicosis in heifers, no adverse reproductive effects could be detected from gossypol intake.

In vitro gossypol induced spermatozoa motility alterations in rabbits

The objectives of the present study were to: (i) examine the in vitro dose response of rabbit spermatozoa motility to the antifertility agent gossypol (GOS) and (ii) determine whether filtered (FIL) and unfiltered (UNFIL) GOS differ in their magnitude of effect. Rabbit semen belonging to adult males (n = 5; 12-14 months) were cultured with UNFIL GOS and FIL GOS (5% solution) and subsequently diluted (1:1-7) for analysis using a Computer Assisted Semen Analyzer (CASA) system in 5 time periods (0, 60, 120, 180 and 360 minutes). At Time 0, no significant change in rabbit spermatozoa motility (MOT) and progressive motility (PROG) with GOS FIL was noted, while increases were observed with GOS UNFIL. At Time 60, weak changes were noted for MOT and PROG. After 120 minutes of culture with both GOS FIL and GOS UNFIL, MOT and PROG decreased significantly in some experimental groups. However, no differences were recorded for both the parameters at Times 180 and 360, with the exception of PROG in the GOS UNFIL category (groups A, B, E, F and G), where a significant decrease was noticed. Detailed evaluation of the distance and velocity parameters revealed reduction in all these studied markers after 60 and 120 minutes of in vitro culture with both GOS FIL and GOS UNFIL, indirectly confirming the PROG decrease. Straightness (STR), linearity (LIN), wobble (WOB), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF) mostly remained unaltered at all time periods for GOS FIL, where as some minor alterations were noticed in GOS UNFIL category for STR, LIN, WOB, ALH and BCF parameters at Time 0, 60 and 120. The present study confirms the dose and time dependent alterations of rabbit spermatozoa motility parameters by GOS. The GOS dynamics in our experiment shows that rabbit spermatozoa as a biological material can indicate a GOS inhibition of motility. Obtained data for the first time indicates a higher immobilizing potential of unfiltered GOS in comparison to filtered GOS in its inhibitory action of spermatozoa motility parameters in rabbits.

Effect of Gossypol in Association with Chromium Protoporphyrin on Heme Metabolic Enzymes

Gossypol prevents the liberation of oxygen from oxyhemoglobin and exerts a hemolytic effect on erythrocytes. In excessive dosages of gossypol, an extreme burden is placed upon the respiratory and circulatory organs owing to the reduced oxygen carrying capacity of blood. Chromium protoporphyrin (CrPP) has been shown to either competitively suppress or to significantly ameliorate a variety of naturally occurring or experimentally induced forms of jaundice in animals and man. In this communication, a novel tissue dependent response to gossypol (50 micromol/kg bw) and gossypol in association with CrPP (50 micromol/kg bw) is described. Our results revealed that gossypol stimulated the hepatic, splenic, and renal delta-aminolevulinic acid synthase (ALA-S) activity, the heme biosynthetic enzyme, and simultaneous administration of CrPP and gossypol synergized the gossypol-mediated increase of ALA-S activity. Gossypol was found to be a potent stimulator of heme oxygenase (HMOX) activity in rat liver and kidney to varying degrees. This tissue response contrasted with that of the spleen, where gossypol decreased the activity of the enzyme. In consonance with the increased hepatic and renal HMOX activity, a marked increase was observed in total serum bilirubin concentration in gossypol treated rats. When rats were given CrPP simultaneously with gossypol, the gossypol mediated increase in hepatic and renal HMOX activity was effectively blocked. Furthermore, the increase in enzymatic activity was accomplished by a decline in the total microsomal protein content on gossypol administration. These findings emphasize the toxic effect of gossypol in eliciting increased heme degradation by stimulating HMOX activity in the liver and the kidney and the potential usefulness of CrPP in experimental and perhaps clinical conditions in which hyperbilirubinemia occurs.

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.

Gossypol--a polyphenolic compound from cotton plant

Gossypol (C(30)H(30)O(8)) is a polyphenolic compound derived from the cotton plant (genus Gossypium, family Malvaceae). The presence of six phenolic hydroxyl groups and two aldehydic groups makes gossypol chemically reactive. Gossypol can undergo Schiff base formation, ozonolysis, oxidation, and methylation to form gossypol derivatives. Gossypol and its derivatives have been the target of much research due to their multifaceted biological activities including antifertility, antivirus, anticancer, antioxidant, antitrypanosomal, antimicrobial, and antimalarial activities. Because of restricted rotation of the internaphthyl bond, gossypol is a chiral compound, which has two atropisomers (i.e., (+)- and (-)-gossypol) that exhibit different levels of biological activities. This chapter covers the physiochemical properties, analyses, biological properties, and agricultural and clinical implications of gossypol.

Reproductive toxicity of lapachol in adult male Wistar rats submitted to short-term treatment

Lapachol is a therapeutic naphthoquinone, but little is known about its general and reproductive toxicity. In female rats, a high incidence of resorptions and fetal mortality has been reported. This work analyses the effect of the short-term administration of lapachol on vital and reproductive organs, and sperm production in Wistar rats. Adult animals were treated with 1 mL of lapachol hydroalcohol solution (100 mg/kg of body weight) for 5 days and killed 3 (T1) and 14 days (T2) after the end of treatment. Body and organ weights and sperm production were evaluated. The administration of lapachol significantly reduced the weight of the seminal vesicle (T1 animals). No significant alteration of gamete production, body weight and the weight of the other organs analysed were detected. The results suggest a reproductive toxicity effect of lapachol, indicating the seminal vesicle as a possible target organ.

Epididymis-Specific Pathologic Disorders in Rats Exposed to Gossypol from Weaning Through Puberty

Previous work in our laboratory revealed that the pubertal period of reproductive development in the male rat was particularly vulnerable to gossypol exposure, with a higher frequency of round structures in the lumen of the cauda epididymidis in the treated rats. Herein, we utilized hemicastration and electron microscopy to confirm that the epididymis is a definitive target of gossypol. Although exposure to gossypol from weaning through puberty caused a significant decrease in daily sperm production, as well as in the concentration of sperm in the epididymis, serum testosterone levels and reproductive organ weights were not altered. In gossypol treated rats, sperm morphology was compromised severely, but the epithelium in testis and epididymis appeared morphologically normal. Ultrastructural examination revealed that round structures, present only in gossypol exposed males, represented: (1) principal cells exfoliated from the epididymal epithelium; (2) epididymal epithelial cell cytoplasm containing degenerating sperm; and (3) degenerating epithelial cells, consisting of vesicles and particles of different sizes, forms and densities. Taken together, the data confirm that gossypol targets the epididymis, disturbing both the structure and function of this organ, and presumably disrupts sperm maturation.

A review on potentiality of medicinal plants as the source of new contraceptive principles

Recently, a review has already been made on the synthetic contraceptive agents whereas this review embraces the natural contraceptives upto year 2001 with 355 references. It also includes the isolation of their active principles, methods of analysis of active ingredients through TLC, HPLC, their side effects and pharmacological action.

Fetal toxicity of Solanum lycocarpum (Solanaceae) in rats

Lobeira (Solanum lycocarpum) is a Brazilian plant used as a hypoglycemic agent. In this study, the toxic effects of lobeira were evaluated during the fetogenesis period. Twenty pregnant Wistar rats were randomly allocated into two groups: control and treated, which received, via oral gavage, 0.5 ml of distilled water or 100 mg of the lobeira powder/kg of body weight, respectively, during days 17-20 of pregnancy. Maternal toxicity was evaluated by body weight, food intake, piloerection, locomotor activity, diarrhoea and vaginal bleeding. Euthanasia was done on 21st day, when ovaries, fetuses and their respective placentas were removed. Resorptions, live and dead fetuses were recorded. External malformations and fetal body, brain, liver, lung and kidneys were also weighed. No clinical signs of maternal toxicity were observed. The placenta weights of the treated rats were lower than those of the control (P<0.01). Lungs (P<0.01) and kidneys (P<0.02) of the fetuses treated with lobeira were also significantly reduced, suggesting a fetotoxic effect of this plant.

Inhibition of T-type Ca(2+) currents in mouse spermatogenic cells by gossypol, an antifertility compound

Gossypol, a male antifertility compound isolated from cotton, has been proved to inhibit capacitation and the acrosome reaction in human and mammalian sperm. Here, by using whole-cell recording, we observed the effects of gossypol on Ca(2+) and Cl(-) currents in mouse spermatogenic cells obtained by mechanical dissociation. The results showed that gossypol concentration-dependently and irreversibly inhibited T-type Ca(2+) currents in the cells. When the concentration of gossypol was > or =5 microM, the currents were blocked completely. The time to current block was progressively shortened as the gossypol concentration was increased from 5 to 80 microM. Moreover, the drug increased the time constant of inactivation in a concentration-dependent manner, while it did not affect the activation of the current. The inhibitory effect on the T-type Ca(2+) current did not correlate with signaling mediated by G proteins and tyrosine phosphorylation. No obvious effect of gossypol on Cl(-) currents was observed. These data suggest that the gossypol-induced inhibition of T-type Ca(2+) currents could be responsible for the antifertility activity of the compound, indicating a possibility to use gossypol as a local contraceptive drug.

The rabbit as a model for reproductive and developmental toxicity studies

The rabbit has many advantages as a nonrodent and second model for assessing the effects of toxic agents on semen quality, fertility, developmental toxicity, and teratology. The male and female reproductive systems of the rabbit are described, and data on growth, sexual development and reproduction are compared with mice, rats, and humans. Techniques for semen collection and evaluation in the male, and artificial insemination, superovulation, embryo culture, and embryo transfer in the female are included as useful procedures in toxicity testing. Examples of the use of rabbits and experimental replication for toxicity testing are given. Special features of the visceral yolk sac and development of the chorioallantoic placenta of the rabbit are compared with rodents. The rabbit extraembryonic membranes more closely resemble the human than do the rodents, in some respects. The use of the rabbit in developmental toxicity and teratology studies is discussed.

Evaluation of the toxicity of Solanum lycocarpum in the reproductive system of male mice and rats

Powdered Solanum lycocarpum fruit is commonly used to treat diabetes, but apparently no studies have been conducted to evaluate potential adverse side effects. In the present paper the toxic effect of S. lycocarpum was evaluated in adult male Wistar rats and Swiss mice. The administration of an aqueous extract prepared using a powder obtained from the S. lycocarpum fruit at two different dose levels (60 mg/15 ml and 120 mg/15 ml distilled water for rats and 30 mg/15 ml and 60 mg/15 ml distilled water for mice, twice daily for 5 days in each case) did not produce body weight variations in either species although a significant weight change was observed in some organs. Significant weight loss was observed only in the ventral prostate of mice receiving the high dose treatment. These results suggest a toxic effect of S. lycocarpum on the male reproductive system of the Swiss mouse, with possible antiandrogenic activity, but there was no apparent antifertility activity in rats at the doses given.

Inhibition of hamster sperm acrosomal enzyme by gossypol is closely associated with the decrease in fertilization capacity

To elucidate the mechanism of sterility induced by gossypol, we studied the relationship between the activities of acrosomal enzymes and their fertilizing capacity in the hamster. The results showed that the ability of spermatozoa to penetrate into bovine cervical mucus, hyperactivated motility (HAM) and fertility in vivo were significantly inhibited when spermatozoa were exposed to gossypol (2.5 microg - 60 microg/mL) for 15 min in vitro. Also, following administration of gossypol (12.5 mg/kg/day) for 6 weeks, sperm motility, HAM and rate of fertilization in vitro by the hamster cauda epididymal spermatozoa were significantly decreased and the extracts of testis delayed dispersion of the cumulus oophorus cells, suggesting that hyaluronidase and other acrosomal enzymes might be inhibited by gossypol. In addition, acrosin and arylsulfatase activities were also markedly inhibited. These data show that the inhibition of acrosin and arylsulfatase activities is the main cause of gossypol-induced infertility. The inhibition was dependent upon gossypol dose and the duration of administration. Thus, the assay of acrosin and arylsulfatase activities may provide a useful tool for monitoring sterility induced by gossypol.

Effects of gossypol on sperm viability and plasma sex steroid hormones in male sea lamprey, Petromyzon marinus

Male sea lampreys Petromyzon marinus were injected with different doses of gossypol acetic acid in an attempt to sterilize them for use in a program for controlling the sea lampreys through the release of sterile males. Two lots of sea lamprey were used in these experiments. The first lot was divided into three groups and fish were injected intraperitoneally (i.p.) with 0.2 ml 50% ethanol as a control group or with gossypol suspended in ethanol at 100 and 200 mg/kg. The second lot was also divided into three groups and fish were either injected i.p. with vehicle as controls or gossypol at 25 and 50 mg/kg. Sperm weight, concentrations and motility were recorded after 31, 36 and 40 days or 24, 28 and 33 days in lots 1 and 2, respectively. Blood was collected from the caudal vessel prior to injections with gossypol and after 40 or 33 days in lots 1 and 2, respectively. Plasma levels of estradiol-17beta (E2), testosterone (T), progesterone (P) and 17,20beta-dihydroxy-4-pregnen-3-one (17,20betaP) were measured by radioimmunoassay. At the end of the experiment, the testis were removed and fixed in Bouin's solution for histological examination. High mortality was observed at the day of injection in the group treated with 200 mg/kg (84.6%), 100 mg/kg (41.7%), and 50 mg/kg (25%). Sperm concentrations were higher in control fish in comparison to most of the treated groups during the first sperm sampling (day 31 or 24), but then differences disappeared. At each sampling, sperm motility was higher in control groups than in treated groups and significant differences were observed (e.g. between control and 50 mg gossypol/kg). Fertility, evaluated at optimized sperm/egg ratio (5 x 10(4) sperm/egg) did not differ among treatments and controls. Changes in mean plasma sex steroid levels in the various treated groups were not significant, but a trend of decreasing plasma E2 was observed with increasing dose of gossypol. The structure of the testis was examined at the end of the experiment using light microscopy and appeared to be unchanged in gossypol-treated lampreys as compared to that of control animals. These findings suggest that gossypol injection into lamprey interferes with some of the reproductive parameters. Although high mortality rate precludes a single i.p. injection of gossypol as a favorable mode of chemosterilization in the lamprey, it would be useful to reassess the means of transfer of gossypol to reproductive tissues. This notion is further supported by the results of an in vitro sperm toxicity assay which revealed that gossypol, at a dose of 100 microM, has an antifertility action in this species.

The antifertility agent, gossypol, releases calcium from rat liver mitochondria

1. The effect of gossypol in the presence of K+ or Ca2+, or both, was studied on respiration, ATPase activity, and Ca2+ transport of rat liver mitochondria. 2. The uncoupled respiration induced by gossypol was inhibited by Ca2+. 3. This inhibition was lowered by the presence of Mg2+. ATPase activity was stimulated when gossypol and Ca2+ were in the incubation medium, in a Ca(2+)-dose related fashion. 4. Mitochondrial Ca2+ was released by gossypol, an effect associated with the membrane fluidity. 5. The results suggest that gossypol modifies the mitochondrial concentration of Ca2+.

Immunoneutralization of gonadotropin-releasing hormone and subsequent treatment with testosterone Silastic implants in rats: an approach toward developing a male contraceptive

STUDY OBJECTIVE

To determine the extent to which increasing doses of exogenous testosterone (T) administered via Silastic implants can restore spermatogenesis and fertility to rats made azoospermic by active immunization against gonadotropin-releasing hormone (GnRH).

DESIGN

Male rats were made azoospermic by active immunization against GnRH. Increasing doses of exogenously administered T (via Silastic implants) were administered for 8 weeks, and testicular sperm concentration and ability to impregnate female rats were evaluated.

SETTING

Reproductive Endocrinology Laboratory, Department of Obstetrics and Gynecology, University of Colorado Health Sciences Center, Denver, Colorado.

ANIMALS

Sexually mature male Sprague Dawley rats (SASCO, Omaha, NE).

RESULTS

Suppression of gonadotropins and azoospermia was achieved by actively immunizing rats against GnRH. Testosterone was capable of restoring quantitatively complete spermatogenesis and fertility in GnRH-immunized azoospermic rats. This relationship was dose-dependent, as evidenced by the partial restoration of spermatogenesis and fertility observed in animals replaced with smaller T Silastic implants.

CONCLUSION

Gonadotropin-releasing hormone immunization and T-filled Silastic implants may provide a model to study isolated gonadotropin deficiency and for the development of a reversible male contraceptive.

Histopathological and biochemical effects of gossypol acetate on pituitary-gonadal axis of male albino rats

Histopathological and biochemical effects of gossypol acetate (GA) on pituitary-gonadal axis were investigated. 10 and 25 mg GA/kg were administered orally to sexually mature adult male Wistar rats for 4 and 5 weeks, respectively. STH and LTH/PRL cells showed no significant changes as compared to those of controls while TSH cells showed hypertrophy, hyperplasia and degranulation in both experimental groups. Pituitary FSH, LH/ICSH cells showed progressive regression. Gonosomatic indices of sex accessory glands at 25 mg showed significant reduction in the experimental animals as compared to those of controls. The diameter of seminiferous tubules reduced and azoospermia developed. Sertoli and Leydig cells also regressed. At 10 and 25 mg GA treatment, spermatogenesis ceased at secondary spermatocytes and spermatogonia stages, respectively. Epididymis and prostate regressed. Seminal vesicle showed no significant histological variations as compared to that of control except reduction in secretion. Biochemical observations revealed increased levels of acid phosphatase, fructose and citric acid and significant reduction in glycerylphosphoryl choline in reproductive glands of both experimental groups as compared to those of controls. Possible mechanism of antifertility action of GA is discussed.

Transfer of 3H-gossypol to neonatal rats via milk of nursing dams

Gossypol is a naturally occurring toxin with potent antifertility action in both males and females. Transfer of gossypol via milk from lactating mother to neonates has not been documented. One theory for the lack of such a finding is that gossypol, once tightly bound to milk proteins, is not extractable by conventional extraction methods for HPLC analysis. This study was designed to examine the possibility and dynamics of transmammary transfer of radioactively-labelled gossypol to neonates through nursing. Nursing rats were dosed with fifty microCi of 3H-gossypol in 0.5 ml of dimethyl sulfoxide via oral intubation on Day 10 post-partum. Six hours after treatment, significant amounts of 3H-gossypol were detected in the coagulated milk collected from the stomachs of the neonates as well as in the blood, liver, lung, spleen and a number of other tissues of these pups. While most neonatal tissues showed a steady decline in 3H-gossypol retention over time regardless of neonatal gender, adrenal glands and gonads preferentially accumulated 3H-gossypol in a time- and sex-dependent manner during the 24-hour sampling period. The results demonstrate that 3H-gossypol is transferred via milk from the nursing dams to their neonates. Thus, the gossypol content of milk presents a conceivable threat to neonatal health, especially to the normal function of steroidogenic organs.

Inhibition of rat embryo implantation in the gossypol-treated uterine horn

We have developed a method to test the effect of gossypol on prevention of embryo implantation in the uterine horn. On the day of proestrus, gossypol (at a dose of 50, 100, 150, 200 and 500 mug per uterine horn was injected directly into the lumen of the right uterine horn. The left uterine horn was injected with 100 mul buffer. The rats were then mated with fertility proven males on the same day. The day of sperm-positive vaginal smear was designated as Day 0 of pregnancy. The number of implantation sites in both control and gossypol-treated horns was examined on Day 8 of pregnancy by laparotomy. The number of pups born was counted after parturition. At laparotomy, the percentages of pregnant animals with positive implantation sites in the gossypol-treated uterine horn (at a dose of 500, 200, 150, 100 and 50 mug per uterine horn) were 0, 0, 0, 10 and 44%, respectively. By contrast, implantation sites were present in 100% of the control horns of the same rats. The average numbers of total implantation sites in both horns vs the number of pups born to gossypol-treated animals using 500, 200, 150, 100, and 50 mug doses were 5.60 +/- 1.25 vs 4.00 +/- 1.00, 5.83 +/- 1.30 vs 4.70 +/- 1.10, 5.80 +/- 1.10 vs 5.50 +/- 1.20, 11.50 +/- 1.00 vs 9.50 +/- 1.50 and 11.67 +/- 1.20 vs 9.30 +/- 1.20, respectively. Gossypol metabolite completely inhibited embryo implantation when administered at 5.30 mug per uterine horn. The potency of the gossypol metabolite in preventing embryo implantation is estimated to be at least 28 times higher than the parent compound.

Gossypol pharmacokinetics in mid-lactation Brown Swiss dairy cows

A bolus equivalent to 450 ppm (dosage based on average feed intake for lactating dairy cows of similar mass) of gossypol was administered orally to three Brown Swiss dairy cows in mid lactation daily for a 7-day treatment period. Blood samples were taken during a 2-day pretreatment period, the 7-day treatment period and a 6-day recovery period. The serum recovered from the cows was stored at -20 degrees C until analysis for extractable gossypol content. The highest concentration of gossypol (a mean of 0.53 microgram/ml serum) was attained in all the cows on day 6 of the treatment period, indicating that a steady-state condition had been reached before the end of the treatment period. The gossypol concentrations then gradually declined during the 6-day recovery period but never fell to the zero baseline. The cows exhibited terminal elimination half-lives of 67, 67.5 and 40 h. Gossypol elimination was best described by a bi-exponential decay curve in two cows and a mono-exponential decay curve in the remaining cow.

Gossypol-induced inhibition of glucose uptake in human ejaculated spermatozoa may be mediated by lipid peroxidation

Gossypol, a plant-derived polyphenolic compound known to exert contraceptive actions in men, inhibits 14C-glucose uptake in vitro in human ejaculated spermatozoa. Spermatozoal glucose uptake was found to increase monotonically up to 40 min, and then decreased by 60 min, possibly because of the saturation of the transport loci in the membrane. Gossypol at the concentrations of 5 and 10 microns caused a reduction of both the linear portion of the uptake and the fall afterwards. Gossypol similarly affects both the Na-dependent and -independent glucose uptake. The kinetic parameters of glucose uptake indicate that gossypol might be interfering with the transport/carrier protein as reduction in maximum uptake velocity (Vmax) was observed without any change in the affinity constant (Km). Similarly, gossypol also produced an increase in spermatozoal lipid peroxidation as evidenced by a steep rise in thiobarbituric acid reaction products in the human sperm cells. A significant decrease in total phospholipid level and the individual classes was noted after gossypol addition. Gossypol-induced inhibition of glucose uptake may be related to the generation of lipid peroxides and consequent membrane damage.

Inhibition kinetics of NAD-linked enzymes by gossypol acetic acid

Effects of gossypol on human spermatozoal enzymes were investigated. This compound was found to be a potent inhibitor of the NAD-linked enzymes, glucelaldehyde-3-phosphate dehydrogenase (GA3PDH), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and isocitrate dehydrogenase (ICDH). MDH was inhibited by gossypol when the reaction was carried out in malate-oxalacetate (direct) or oxalacetate-malate (reverse) directions. The I50 of gossypol for the direct reaction was 2.9 microM, whereas that for the reverse reaction was 1.2 microM. Reciprocal plots due to Lineweaver-Burk showed that MDH is inhibited in a noncompetitive manner with respect to both reactions. LDH was also inhibited by this compound when pyruvate or alpha-ketobutyrate was used as a substrate. Gossypol was a noncompetitive inhibitor for LDH. The I50 of gossypol for LDH were 9.8 microM and 11.3 microM, when using pyruvate and alpha-ketobutyrate, respectively as substrates. The I50 of gossypol for GA3PDH and ICDH were 110 microM and 2.7 microM, respectively.

Limitations in developing gossypol acetic acid as a male contraceptive

Highly purified gossypol acetic acid (5 mg/day; oral) alone and in combination with potassium chloride (0.25 mg/day; oral) was tested in adult male langurs for 120 days to evaluate reversibility of its antifertility action and possible hypokalemia. The treatment resulted in severe oligospermia with impairment of sperm motility. Sperm morphological defects were evident. The functional activities of accessory sex glands and libido remained unimpaired. Occurrence of hypokalemia was found more pronounced in the gossypol alone group. Extensive renal potassium loss was evident and conversely the renal excretion of sodium decreased markedly. The activities of serum transaminases increased significantly. Other parameters of blood and of urine did not show any marked alterations. Complete reversal of the above changes was evident following 90 to 105 days of withdrawal of treatment. In conclusion, the oligospermia achieved was reversible and the hypokalemic response of langurs is similar to human and not related to impurity of the drug.

Effects of gossypol on the motility of mammalian sperm

The effects of the male contraceptive gossypol on the motility of mammalian spermatozoa are reviewed. The role of sperm motility in the processes of fertilization and the effect of the drug on these processes determine its effectiveness as a contraceptive. The promising male contraceptive potential of gossypol is discussed in the context of the serious adverse effects of the agent.

High susceptibility of five axenic Entamoeba histolytica strains to gossypol

The antiamoebic potency of gossypol was tested against 5 axenic Entamoeba histolytica strains, in logarithmic phase growth in PEHPS medium. All of the strains were moderately susceptible to this polyphenolic drug. The 50% inhibitory concentration (IC50) was of the same order of magnitude in all strains: 0.015 microM (for strain HM-1) to 0.067 microM (for HM-38). The difference between the IC50 of HM-1 and the remaining 4 strains (HM-38, HK-9, HM-2 and HM-3) was significant, although it was greater between HM-1 and HM-38 (P less than 0.005) than between HM-1 and the other 3 strains (P less than 0.05), for which the IC50 was 0.03 microM, 0.049 microM and 0.38 microM respectively. Gossypol is more toxic in vitro for amoebae than other drugs widely used clinically, its pharmacological effects and safe dosage in humans are well known because of its antifertilizing effect, and it is accumulated mainly in the liver and colon. Accordingly, this compound could be a good antiamoebic agent if it is as potent in vivo as it is in vitro.

Inhibitory effects of gossypol analogs on human sperm motility

Aqueous-soluble gossypol Schiff's bases, SP562: bis-8,8'-[(N-(2-(dimethylamino)ethyl]-iminomethylene]- [1,1',6,6',7,7'-hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2- binaphthalene dihydrochloride; SP563: bis-8,8'-[(N-(2-(diethylamino)ethyl]-iminomethylene]-1,1',6,6',7,7 '- hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2'-binaphthalene++ + dihydrochloride; and SP564: bis-8,8'-[(N-(2-(diethylamino)propyl]-iminomethylene]- 1,1',6,6',7,7'-hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2'- binaphthalene dihydrochloride, were investigated for their effects on human sperm motility. SP564, which has the longest alkyl substituent of the Schiff's base, appeared to exert the greatest inhibitory effects on human sperm motility. These inhibitory effects were even greater than those caused by (+/-)gossypol acetic acid at the same concentration.

Incorporation of gossypol and formation of its protein conjugates in mouse transformed Sertoli (TM4) cells

Mitochondria of both mouse transformed Sertoli (TM4) cells and primary-cultured rat and mouse Sertoli cells were shown to be preferentially affected by gossypol (Tanphaichitr et al, 1984). To investigate whether this selective effect was due to a greater of TM4 cells to accumulate gossypol, TM4 and other somatic cell lines, including dog (MDCK) and kangaroo (PtK2) kidney epithelial cells, rat embryo fibroblasts (Rat-1) and mouse BALB/c 3T3 fibroblasts, were incubated with [14C]gossypol and the incorporated specific activity of the drug was assessed. The results indicate that TM4 cells accumulated [14C]gossypol at the highest level. Incorporated [14C]gossypol appeared to bind to TM4 cell macromolecules and remained in the dialysis tubing after extensive dialysis. Characterization of these gossypol-conjugated proteins by SDS-polyacrylamide gel electro-proteins had apparent Mr's of 92,500, 70,000, 63,200, 60,000, 58,100, 54,000, 52,000, 50,000, 47,500, 40,000 37,000, 35,000, 30,000, 20,000, and 14,500 daltons. Conjugation of these proteins with gossypol may result in macromolecular dysfunction and abnormal structure.

Effect of gossypol and its metabolite on in vitro early development of mouse embryos

The purpose of this study was to examine the effect of gossypol and its metabolite on early in vitro mouse embryo development. One hundred and thirty-eight excellent quality mouse blastocysts were randomly assigned to five different treatments. Culture media were supplemented with 10% (V/N) normal steer serum. The embryos were cultured at 37 degrees C with an atmosphere of 5% O(2), 5% CO(2) and 90% N(2), and embryo development was examined and recorded at 12-h intervals for 72 h. The percentage of embryos that developed to expanded blastocyst (92%), hatching blastocyst (84%), and hatched blastocyst (76%) stages in control Ham's F-10 media was not different from that of embryos cultured in media containing 0.1 and 5 mug of gossypol; however, none of the embryos treated with 265 ng of gossypol metabolite (GM) developed beyond the blastocyst stage. A substantial decrease in the percentage of embryos reaching hatching blastocyst (29%) and hatched blastocyst (29%) stages was observed in the embryos cultured with 5.3 ng of GM. At both light and electron microscopic levels, the embryos appeared to be affected even by a lower concentration of GM in vitro. Our results suggest that GM has a much greater potency than the parent gossypol in inhibiting the early development of mouse embryos in vitro.

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.

Gossypol inhibition of Ca++ uptake and Ca++-ATPase in human ejaculated spermatozoal plasma membrane vesicles

Gossypol, a plant-derived polyphenolic compound known to exert contraceptive actions in men, inhibits Ca++-transport and Ca++-activated ATPase in isolated plasma membranes of ejaculated human sperm cells. It also inhibits the membrane bound Mg++- and Na+ + K+-dependent ATPases, 5'-nucleotidase and alkaline phosphatase systems. Ca++-ATPase inhibition by gossypol is non-competitive. It abolishes the discontinuity in Arrhenius expression of temperature dependence of Ca++-ATPase and increases the energy of activation. Phosphatidyl choline and Na+-deoxycholate inhibit Ca++-transport activity in the membrane vesicles. The apparent similarity of Ca++-transport inhibition by gossypol and phosphatidyl choline may indicate the possible capability of this compound to induce changes in the lipid microenvironment of the membranes, wherein the integral proteins operate. Inhibitory effect of gossypol on the plasma membrane Ca++-pump suggests that gossypol may affect sperm motility by a mechanism which is related to the structure and functions of the plasma membrane.

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.

Effects of diets containing gossypol on spermatogenic tissues of young bulls

Eighteen yearling beef bulls were used in a study to determine the effects of diets containing gossypol on spermatogenic tissues, Sertoli cells and Leydig cells. Bulls were randomly assigned to one of three (n = 6) isonitrogenous diet groups formulated from alfalfa hay and corn (gossypol-free control), control plus whole cottonseed and cottonseed hulls, or control plus cottonseed meal and cottonseed hulls as sources of gossypol. Testicular tissues collected were examined histologically, and tissues from bulls fed gossypol-free diets were compared with those fed diets containing cottonseed products. Following a 2-mo period (P(1)) when bulls were fed diets containing gossypol, one-half of the bulls were placed on a gossypol-free diet for an additional 2 mo (P(2)) to determine if gossypol effects were reversible. At the end of P(1), bulls fed whole cottonseed and cottonseed meal had larger (P<0.01) lumens in their seminiferous tubules, decreased (P<0.001) wall thickness in their seminiferous tubules, and a reduced (P<0.0001) number of cell layers in their seminiferous tubles, when compared with bulls fed a gossypol-free diet. These histological changes indicate detrimental effects to the spermatogenic tissues and associated cells. Following the initial two months (P(1)) of receiving feed containing gossypol, herd mates that were fed a gossypol-free diet for 2 mo (P(2)) showed improvement in histological characteristics, indicating that gossypol-induced effects were partially reversible.

Effect of gossypol on bovine embryo development during the preimplantation period

The purpose of this study was to evaluate the effect of varying doses of gossypol acetic acid on early bovine embryo development in vitro. One hundred and forty-eight excellent and good quality bovine morulae were randomly cultured in 0, 1.0, 5.0, 10.0, 30.0 mug gossypol acetic acid (GAA) in normal steer serum and Ham's F-10 media. Bovine embryo development was assessed at 12-h intervals for 96 h. Sixty-seven percent of embryos developed in 0 mug GAA to the hatched blastocyst stage, while 43, 19, 4 and 0% had comparable development in 1.0, 5.0, 10.0 and 30.0 mug GAA, respectively. Embryos in 5.0 mug GAA had a delayed development to the blastocyst stage compared to embryos in 1.0 mug GAA. Development time to expanded blastocyst stage was longer for 10.0 mug GAA embryos than 0, and 1.0 GAA-treated embryos. No embryo cultured in 30.0 mug GAA advanced past the morula stage. Final developmental scores were highest for embryos in 0 mug GAA (4.06) and lowest for embryos cultured in 10.0 and 30.0 mug GAA (0.44 and -0.02, respectively). Embryos cultured in higher doses of GAA degenerated sooner than embryos cultured in 0 mug GAA. These data show a dose-dependent detrimental action of GAA on early bovine embryo development and suggest a direct action on the embryo itself.

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.

Studies of the mechanism of action of gossypol as a male antifertility agent

Gossypol administered orally to male rats at a daily dose of 20 mg/kg body weight for 62 days caused infertility. There were changes in the epididymal epithelium and the sperm were severely damaged and immotile. The sperm head was often detached; other defects were abnormal mitochondria, absence of plasma membranes and axonemal and accessory fibres and a lower oxygen uptake. To study the effect of gossypol on the motor apparatus of sperm, ram sperm were demembranated with the detergent, Triton-X-100. Such sperm models can normally be reactivated with ATP but gossypol (2.5-12.5 microM) decreased reactivation and must have a direct effect on the axoneme. Gossypol also inhibited ram sperm adenyl cyclase which is essential for maintaining high levels of cAMP in sperm and, in turn, motility. Ram sperm adenyl cyclase required Mn2+ for activity and high Mn2+ concentrations protected the enzyme from gossypol inhibition. Electron spin resonance studies proved that gossypol chelated Mn2+ with the formation of a 2:1 complex.

Sites of action of gossypol studied by autoradiography and enzyme histochemistry

The distribution of 14C-gossypol acetate was studied by autoradiography in male rats after intraperitoneal or intratesticular injection. Accumulation of radioactivity was found in testis, kidney and liver, while there was little in brain, pituitary and epididymis. In testis, high accumulation occurred in interstitial cells, with low levels in Sertoli cells, spermatogonia and spermatocytes. In addition, the chronic effect of gossypol was assessed by enzyme histochemistry with thiamine pyrophosphate, alpha-glycerophosphate dehydrogenase, and by lipid stain. In the treated animals an increased number of luminal exfoliated cells (Sertoli cells, germ cells and spermatids) was noted, which showed positive reactions. The results suggest both direct and indirect effects of gossypol on testicular functions.

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.

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.

Effects of gossypol on the antioxidant defense system of the rat testis

This study examined the effects of gossypol acetic acid on the antioxidant defense system of the rat testis. In gossypol-treated animals testis catalase and glutathione peroxidase activities were decreased. Catalase and glutathione peroxidase are the two enzymes that protect against oxidative damage by hydrogen peroxide. Other antioxidants that were reduced in treated animals were glucose-6-phosphate dehydrogenase, superoxide dismutase, glutathione reductase, alpha-tocopherol, and ascorbate. Gossypol, a pigment of cottonseed and cottonseed products, causes infertility in humans and many animal species, but its mechanism of action is unknown. Gossypol is known to produce reactive oxygen species in vitro. Oxidative injury caused by the generation of reactive oxygen species and a compromised antioxidant defense system may be responsible for the antifertility effects of gossypol.

Antifertility effect of gossypol in male Japanese quail

Conventionally housed 130-160 g adult male Japanese quail were given gossypol acetic acid (gossypol) im at 25 mg/kg in 0.5 ml of 10% EtOH for 12 and 24 days (Groups 1 and 2), respectively. One day after treatment was terminated they were allowed to mate with laying females individually for 20 days. Fertility was 0% from mating of the Group 1 birds on days 1-2 and increased to 25, 35, 55 and 65% on days 3-6 after cessation of gossypol treatment. At day 11, fertility was 80 vs 84% in controls, whereas hatchability was 70% for both. By comparison, eggs from Group 2 mated quail were infertile for up to 20 days after the termination of gossypol treatment. In a parallel experiment, the percent testes to body weight ratio in control and 7, 14, 21, and 28-day gossypol-treated quail was 2.5, 2.2, 1.8, 0.5, and 0.2%, respectively. In 12 vs 24-day treated birds, 7, 14, 21, and 28 days after gossypol treatment, the ratios were 1.0 vs 0.5%, 2.0 vs 0.8% and 2.8 vs 1.9%, respectively. The decreased fertility and hatachability, and testicular atrophy resulting from gossypol given to male quail was dose-time related. Furthermore, the androgen-dependent cloacal gland was drastically reduced in size by the treatment with gossypol. The mode of action of gossypol in male quail is different than it is in mammals in that the testicular size of mammals remains unchanged with long-term gossypol treatment. It is concluded that quail may be a useful avian animal model for investigating the antifertility effects of gossypol.