Studies on the male antifertility agent-gossypol acetic acid. II. Effect of gossypol acetic acid on the motility and ATPase activity of human spermatozoa

Antioxidant additive melatonin in tris-based egg yolk extender improves post-thaw sperm attributes in Hariana bull

In the study, melatonin, a known antioxidant pineal peptide was used as an additive in the tris-egg yolk glycerol-based semen extender in Hariana bull semen and post-thaw sperm characters were evaluated. In the study, Group I was a control without melatonin; and Group II, III, and IV were having 0.5 mM, 1 mM, and 2 mM melatonin/80 × 10⁶ spermatozoa, respectively were treatment groups. Thirty-two semen ejaculates from 4 Hariana bulls were processed for freezing and post-thaw sperm characteristics were evaluated. Sperm motility, velocity, the viability with intact membrane, and total antioxidant capacity were markedly (P < 0.05) improved in Group IV compared to all other groups. The lipid peroxidation and total protein carbonylation were substantially (P < 0.05) decreased in Group IV compared to all other groups. The population of cryocapacitated, acrosome-reacted, and apoptotic-like spermatozoa were significantly (P < 0.05) decreased in Group IV. Further, the relative band intensity of 74 kDa protein and percent of spermatozoa showing positive immune reactivity to tyrosine-phosphorylated proteins was decreased in Group IV. The progesterone-receptor ligand binding, in vitro capacitation response, and Vanguard distance were markedly (P < 0.05) improved in Group IV. In summary- Group IV having 2 mM melatonin was found to be optimal in providing cryoprotective effects to Hariana bull spermatozoa after freezing-thawing and can be suitably used as a semen additive during semen cryopreservation.

Resveratrol offers protection to oxidative stress induced by ferrous ascorbate in bovine spermatozoa

Resveratrol (RES) is a natural polyphenol and phytoestrogen exhibiting cardioprotective, anticancer, antibacterial and vasorelaxing properties. It is also a powerful reactive oxygen species (ROS) scavenger and chelating agent. This study was designed to determine the efficiency of RES to reverse the ROS-mediated impairment of the motility, viability and intracellular antioxidant profile of bovine spermatozoa. Spermatozoa were washed out of fresh bovine semen, suspended in 2.9% sodium citrate and subjected to RES treatment (5, 10, 25 and 50 μmol L(-1)) in the presence or absence of a pro-oxidant, i.e., ferrous ascorbate (FeAA; 150 μmol L(-1) FeSO4 and 750 μmol L(-1) ascorbic acid) during a 6-h in vitro culture. Spermatozoa motion parameters were assessed using the SpermVision computer-aided sperm analysis (CASA) system. Cell viability was examined with the metabolic activity (MTT) assay, and the nitroblue-tetrazolium (NBT) test was applied to quantify the intracellular superoxide formation. Cell lysates were prepared at the end of the in vitro experiments in order to investigate the intracellular activity of superoxide dismutase (SOD), catalase (CAT), as well as the concentrations of glutathione (GSH) and malondialdehyde (MDA). FeAA treatment led to a reduced sperm motility (P < 0.001) and viability (P < 0.001), decreased the antioxidant parameters of the samples (P < 0.001 in case of SOD; P < 0.01 with respect to CAT; P < 0.05 in relation to GSH) but increased the superoxide production (P < 0.001) and lipid peroxidation (P < 0.001). RES supplementation resulted in a preservation of the spermatozoa vitality and antioxidant characteristics (P < 0.001 in case of SOD; P < 0.01 with respect to 25-50 μmol L(-1) RES and P < 0.05 in relation to 10 μmol L(-1) RES; P < 0.05 in case of GSH), with 50 μmol L(-1) RES proving to be the most effective RES concentration. Our results suggest that RES possesses significant antioxidant properties that may prevent the deleterious effects caused by ROS to spermatozoa, and preserve the fertilization potential of male reproductive cells.

Effect of ferrous sulphate and ascorbic acid on motility, viability and lipid peroxidation of crossbred cattle bull spermatozoa

Numerous factors influence male fertility, one of these being the oxidative stress, which has elicited enormous interest recently. In sperm, induction of oxidation decreases motility and viability but increases lipid peroxidation (LPO). The optimum dose of ferrous ascorbate (FeAA: FeSO4 + ascorbic acid) for inducing oxidative stress by affecting motility, viability and LPO has been ascertained in local crossbred cattle bull spermatozoa. The fractions of spermatozoa suspended in 2.9% sodium citrate were subjected to three doses of FeAA (100 : 500, 150 : 750, 200 : 1000; μmol/l FeSO4 : μmol/l ascorbic acid). These fractions were assessed for various parameters. Increase in the incubation period and promoter concentration induced a decrease in motility and viability, but an increase in LPO. Among three doses of FeAA, 150 : 750 μmol/l ascorbic acid is suggested to be the optimum/best dose as it induces the oxidative stress/LPO to a significant extent and also maintains better motility and viability as compared with the other two doses, and such conditions may enhance the fertilising potential of bull spermatozoa.

Evaluation of contraceptive activity of methanol extract of Dendrophthoe falcata stem in male albino rats

The present study was undertaken to evaluate the contraceptive efficacy of methanol extract of Dendrophthoe falcata Ettingsh (family-Loranthaceae), stem in male albino rats as reported in folk remedies. Adult proven fertile male rats were gavaged methanol extract of D. falcata stem at 50, 100 and 200mg/rat/day for 60 days. The activity was compared with standard drug, i.e. Lonidamine. On day 61 the animals were autopsied and the testes, epididymides, seminal vesicle and ventral prostate were dissected out and weighed. Sperm motility and density and serum testosterone level were assessed. The sperm motility and density were significantly reduced. The histoarchitecture of testes revealed degenerative changes in the seminiferous tubules, arrest of spermatogenesis at the stage of round spermatid. Serum testosterone levels were decreased significantly in all treatment groups. It is concluded that D. falcata methanol stem extract showed a significant effect on fertility in male rats as reported in folk remedies.

Antispermatogenic, antiandrogenic activities of Albizia lebbeck (L.) Benth bark extract in male albino rats

Methanolic extract of Albizia lebbeck bark when administered orally at the dose level of 100 mg/rat/day to male rats of proven fertility for 60 days did not cause any significant loss in their body weights but the weights of reproductive organs, i.e. testis, epididymides, seminal vesicle and ventral prostate were decreased in a significant manner when compared to controls. Sperm motility as well as sperm density were reduced significantly which resulted in reduction of male fertility by 100%. Marked decline in the germ cell population was noticed. Population of preleptotene, pachytene, secondary spermatocytes and step-19 spermatid were declined by 60.86%, 65.81%, 71.56% and 66.55%, respectively. Cross-sectional surface area of sertoli cells as well as the cells counts were found to be depleted significantly. Leydig cells nuclear area and number of mature Leydig cells were decreased by 60.03% and 51.56%, respectively. Serum testosterone levels showed significant reduction after A. lebbeck extract feeding. Oral administration of the extract did not affect red blood cell (RBC) and white blood cell (WBC) count, haemoglobin, haematocrit and glucose in the blood and cholesterol, protein, triglyceride and phospholipid in the serum. In conclusion, A. lebbeck bark extract administration arrests spermatogenesis in male rats without noticeable side effects.

Effect of benzothiazoline ligand and corresponding organoantimony(V) derivative on the reproductive system of male rats

Benzothiazoline HNC(6)H(4)SC(C6H5)CH:C(OH)COOCH(3) 1 prepared by the condensation reaction of aroyl pyruvate and 2-aminothiophenol has been treated with Ph(3)Sb(OPr(i))(2) to yield Ph(3)Sb[SC(6)H(4)NC(C6H5)CH:COCOOCH(3)] 2. These compounds have been characterized by elemental analyses and molecular weight determinations. The probable structures of the ligand as well as antimony complex have been tentatively proposed on the basis of IR and NMR ((1)H and (13)C) spectral evidences. Both compounds have been tested for their antifertility activity in male albino rats. The oral administration of compounds 1 and 2 at the dose level of 10 mg/rat/day significantly reduced the weights of testes, epididymides, ventral prostate, and seminal vesicles. The production of preleptotene spermatocytes was decreased by 36.57%; 57.23%, pachytene spermatocytes by 40.06%; 62.01%, and secondary spermatocytes by 52.45%; 63.22%, following the treatment of compounds 1 and 2, respectively. The marked reduction in sperm motility and density resulted in infertility by 100%. Significant (P < .01) alterations were found in biochemical parameters of reproductive organs in treated animals as compared to control group. It is concluded that all these effects may finally impair the fertility of male rats.

Assessment of reversible contraceptive efficacy of methanol extract of Mentha arvensis L. leaves in male albino mice

The present study was undertaken to assess the reversible contraceptive efficacy of methanolic extract of Mentha arvensis leaves. Aqueous solution of the extract (10 mg per day per mouse) when administered orally to male mice of proven fertility for 20, 40 and 60 days caused inhibition of fertility while maintaining their normal sexual behaviour. With the increase in treatment duration, there occurred a corresponding decrease in the mean weight of testis and accessory organs of reproduction. Sperm concentration, motility and viability in the cauda epididymis were also decreased. Spermatozoa with coiled tails also appeared in the epididymal smear. However, all the induced effects returned to normalcy within 30 days following withdrawal of 60-day treatment. Oral administration of the extract also did not affect the body weight of the mice and their blood cells count, packed cell volume, haemoglobin and blood/serum biochemistry.

The inhibitory effects of gossypol on human sperm motility characteristics: possible modes of reversibility of those effects

Gossypol (GOS) is a polyphenolic compound derived mainly from cottonseed oil, which has been found to have anti-fertility effects in males. It has been reported to induce disturbances of the hypothalamicpituitary axis, disruption of spermatogenesis in the testes, and inhibition of postejaculatory spermatozoa motility. The inhibition of human sperm motility by GOS has been documented both in vivo and in vitro, although the exact mechanism and possible reversibility of such inhibition is unknown. The objectives of the present study were 1) to examine the in vitro dose response of human sperm motility to GOS, and 2) to determine if the motility inhibition of GOS was reversible, using agents which alter the second messenger cyclic adenosine monophosphate (cAMP), such as, 8-bromo-cAMP (8-Br-cAMP), and forskolin, and adenylate cyclase stimulator. Fresh spermatozoa were obtained from males of known fertility. Motile spermatozoa were recovered via the SpermPrep (SP) method and used further in all experiments. Quantitative and qualitative sperm parameters were recorded at collection, post-SP filtration and post-treatment. Motile spermatozoa were resuspended in either media (SP), or in increasing concentrations of GOS (10, 20, 30 and 50 micrograms/ml) as gossypol acetic acid in media. To study the possible reversibility of the GOS effects, spematozoa already exposed to GOS for 2 hr (at the concentrations mentioned above) were centrifuged and reconstituted in media containing either 10 mM 8-Br-cAMP or 100 microM forskolin and measurements of percent motility and grade of motility (0-4) were taken at 0 time and at 30 min intervals for a total of 2 hr. Each experiment was replicated 8 times. The results obtained in this study showed that GOS inhibited sperm motility in a dose and time dependent manner. The motility characteristics of the 50 micrograms/ml GOS group were lower than all other groups (p < 0.001) and the spermatozoa were completely immobilized within 60 min. Cyclic AMP somewhat rescued the GOS-treated sperm, whereas exposure of GOS-treated sperm to forskolin had no such effects. The data generated in the present study suggest that GOS inhibits cAMP formation, which subsequently decreases sperm motility characteristics. At low concentrations (up to 20 micrograms/ml for 30 min), GOS inhibition is reversibile and compounds that act to increase cAMP seem to be partially responsible for the reversal of GOS inhibition. However, GOS inhibitory effects at levels higher than 20 micrograms/ml (exposed for 30 min) were impossible to reverse, which suggest that GOS at those levels could be an effective agent for vaginal contraception.

The effects of cyclic adenosine monophosphate, forskolin, and theophylline on motility parameters in gossypol-treated human sperm

OBJECTIVE

To examine the effect of gossypol on human sperm in vitro and the mechanism for the effect.

DESIGN

Fresh sperm ejaculates obtained from normal donors to the University of Kentucky Andrology Donor Program were exposed to gossypol. Motility was studied manually and using computer-assisted sperm analysis. In subsequent experiments, the effects of forskolin, theophylline, and cyclic adenosine monophosphate (cAMP) on sperm motion were measured.

SETTING

University of Kentucky Department of Obstetrics and Gynecology Andrology Laboratory.

MAIN OUTCOME MEASURES

Manual and computer-assisted measurements of sperm motility and motion characteristics.

RESULTS

Gossypol inhibited sperm motility, which could be reversed partially by increasing cAMP.

CONCLUSION

Gossypol exposure in vitro adversely affects sperm motility in a dose- and time-dependent manner by a cAMP-dependent mechanism.

Genetic toxicity studies of gossypol

Gossypol, a polyphenolic compound extracted from cotton plants, shows promise for use as a male contraceptive, as well as a treatment for gynecological disorders, cancer, and certain microbial diseases. Before gossypol can be considered safe for widespread human use, particularly by healthy people of childbearing age, its effect on normal genetic processes should be understood. Characterization of gossypol's genotoxic potential has not been approached systematically, although numerous clinical and laboratory studies have addressed issues relating to genetic effects of gossypol. This review summarizes results of relevant studies and offers recommendations for the emphasis of future efforts to understand gossypol's genotoxicity potential. Evidence suggesting that gossypol has any genotoxic effects in mammals under normal physiologic conditions so far is weak, at best. However, several unresolved issues that are important for establishing long-term genetic safety of gossypol were uncovered by this analysis. These include the need for a better understanding of the significance of weak increases in SCE frequency seen in a number of laboratory exposure studies, and more definitive, comprehensive animal tumor bioassay data.

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+.

Behavioral and metabolic interaction between gossypol and ethanol

The effects of gossypol on ethanol-elicited responses pertaining to liver ethanol, acetaldehyde-metabolizing enzymes and alcohol preference were studied in rodents. Intraperitoneal injection of a single dose of gossypol, 100 mg/kg, inhibited hepatic alcohol dehydrogenase for 50 h in mice from both sexes. The acute gossypol treatment produced earlier inhibition of mouse liver cytoplasmic aldehyde dehydrogenase in male than female mice. Acute gossypol administration initially inhibited mouse liver subcellular mitochondrial aldehyde dehydrogenase in both sexes which was not evident 50 h later. Administration of gossypol, 10 mg/kg i.p., to male rats with preference for ethanol caused aversion for ethanol drinking. The enzymatic determinations indicate gender sensitivity of subcellular mouse liver aldehyde dehydrogenase to gossypol. The behavioral study suggests adverse metabolic interaction between gossypol and alcohol which may underlie the rat aversion to voluntary ethanol drinking.

Inhibition of sialyl transferase activity by gossypol acetic acid in human seminal plasma

Seventeen aliquots of 15 microliters seminal plasma of human origin were incubated with 25 micrograms, 15 micrograms, 5 micrograms and 2.5 micrograms gossypol acetic acid (GAA), dissolved in BWW containing 0.9% sodium chloride and 0.9% benzyl alcohol, at 37 degrees C for 60 minutes. Following incubation, activity of sialyl transferase (S.T.) was determined by a procedure involving incorporation of radioactive sialic acid into asialofetuin. The activity of S.T., expressed as cpm per hour per 15 microliters seminal plasma was compared to controls consisting in incubation of sperm in BWW containing 0.9% benzyl alcohol and 0.9% sodium chloride. The activity of S.T. in controls represented 61.3 +/- 8.0%-67.7 +/- 8.9% of the activity obtained by incubation with BWW only. GAA was found to exert a dose-dependent inhibition of S.T. activity, ranging from 38.3 +/- 20.6% to 53.4 +/- 19.4% (with 25 micrograms) and from 11.3 +/- 14.8% to 21.9 +/- 14.8% (with 2.5 micrograms).

Anti-spermatogenic activity of malvidin chloride in langur monkeys (Presbytis entellus entellus Dufresne)

Malvidin chloride (MC) a colouring agent from flowers of Malvaviscus conzattii Greenum was studied for male anti-fertility effects in adult langur monkeys (Presbytis entellus entellus Dufresne). When fed 50 mg MC kg-1 for a period of 60 days, inhibition of spermatogenesis resulted. The weights of testes and epididymides were reduced and there was atrophy of the Leydig cells. In the epididymis, epithelial cell heights were reduced after MC-treatment. Conspicuous shrinkage of seminiferous tubules and Leydig cell nuclei were evident. Depletion of total proteins, RNA, sialic acid, alkaline/acid phosphatase activity in testes and epididymides with the elevation of testicular levels of cholesterol and glycogen also occurred. Blood/serum analysis and haematology of MC-treated langur monkeys revealed that all of the clinically important parameters were well within the normal range. The slightly increased bilirubin concentration and alkaline phosphatase activity returned to normal range within 30 days of the last dose of MC. The anti-spermatogenic activity of MC in langur monkeys is discussed.

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.

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.

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.

Effect of gossypol on spermatozoal lactate dehydrogenase-X (LDH-X) in male rats

The studies in this report evaluate the inhibitory effects of long-term gossypol acetic acid (gossypol) administration on spermatozoal lactate dehydrogenase (LDH-X) activity, fertility and reversibility. Gossypol at 20 mg/kg/day or vehicle only was administered orally to adult male rats for 5 consecutive weeks. Groups of control and gossypol-treated rats were sacrificed at 2-, 4-, and 5-week intervals when LDH-X analysis of spermatozoa were prepared from the tail of the epididymis. An additional group of control and gossypol-treated rats were allowed to recover for up to 8 weeks after withdrawal of the treatment. In the gossypol-treated rats, the spermatozoal LDH-X activity was depressed by 80% of control level after a 5-week treatment period. There was no significant difference in spermatozoal LDH-X activity between the control and treated animals at 2 and 4 weeks. However, the number of ejaculated sperm estimated from the vaginal smear preparations after each mating was significantly less than the control values after 2, 4 and 5 weeks of treatment. At 5 weeks after the cessation of gossypol treatment, the spermatozoal LDH-X activity had only partially recovered but the fertility (number of ejaculated sperm, embryo implantation sites and pups born) had recovered to a level comparable to the control values 5 weeks after the cessation of gossypol treatment. The inconsistencies in the response of spermatozoal LDH-X activity, sperm number and fertility to gossypol may suggest that the antifertility action of gossypol and spermatozoal LDH-X activity in adult male rats may not be directly related as suggested by the results generated from the in vitro studies.

Involvement of prostaglandin in the antifertility effects of gossypol

This study was undertaken to determine the effects of gossypol alone and gossypol in combination with prostaglandin and aspirin. Rats were administered gossypol (40 mg/kg/day), gossypol and prostaglandin (PGF2 alpha-2 mg/kg/day), gossypol and aspirin (300 mg/kg) for 4 weeks. A marked effect of the gossypol-prostaglandin combination was observed on sperm motility and spermatogenesis. The effect of the gossypol-aspirin combination was less pronounced. The ratio of body weight to testicular and epididymal weights between the different groups showed no marked difference. No effect of drug treatment on plasma testosterone, LH and FSH was observed. The data presented in this paper suggest that prostaglandin plays an important role in the antifertility effects of gossypol.

Studies on the male antifertility agent gossypol acetic acid. VII. Effect of motility stimulated factors on the revival of human spermatozoal motility after gossypol treatment in vitro

Human spermatozoa were incubated with gossypol acetic acid (100 micrograms/1 X 10(6) spermatozoa/ml) at 37 degrees C for 30 min. The drug treatment inhibited the spermatozoal motility significantly. Washing of the spermatozoa, after gossypol treatment, did not effect their motility. A partial revival in the motility of the spermatozoa was observed when gossypol treated spermatozoa were incubated, after washing, with motility stimulating factors, e.g. theophylline, dibutyryl-cAMP and Kallikrein.

Morphologic and endocrine changes in the reproductive organs in rats implanted with gossypol acetate pellet in the testis

Gossypol acetate pellets in concentrations ranging from 0.5, 1.0, 5.0, 10.0, to 20.0 mg were implanted in the testis of rats for a period up to 7 weeks. The implant was made in one testis only. In animals with a 10.0-mg implant, the germinal epithelium showed degenerative changes following the 7-week period, but spermatogonia and spermatocytes were unaffected. The effect of gossypol acetate appeared to be at the spermatid level. The electron microscopic study showed that the acrosomal membranes were disrupted. Blood testosterone and LH, but not FSH, decreased significantly (P less than 0.01). The fertility studies showed 100% infertility but no loss in libido in the 10-mg implant group. Up to the 7-week period, implants of less than 10 mg produced no significant effects on any of the parameters mentioned above. Animals with 20-mg implants had toxic symptoms. From the results in this study, it is concluded that 10.0 mg of gossypol acetate implanted in a single pellet in one testis causes antispermatogenic effects.

Inhibition of DNA polymerase alpha by gossypol

Our earlier studies have shown that gossypol is a specific inhibitor of DNA synthesis in cultured cells at low doses. In an attempt to determine the mechanism for the inhibition of DNA synthesis by gossypol we observed that gossypol does not interact with DNA per se but may affect some of the enzymes involved in DNA replication. These studies indicated that gossypol inhibits both in vivo and in vitro the activity of DNA polymerase alpha (EC 2.7.7.7), a major enzyme involved in DNA replication, in a time- and dose-dependent manner. Kinetic analysis revealed that gossypol acts as a noncompetitive inhibitor of DNA polymerase alpha with respect to all four deoxynucleotide triphosphates and to the activated DNA template. Inhibition of DNA polymerase alpha does not appear to be due to either metal chelation or reduction of sulfhydryl groups on the enzyme. Gossypol also inhibited HeLa DNA polymerase beta in a dose-dependent manner, but had no effect on DNA polymerase gamma. These results suggest that inhibition of DNA polymerase alpha may account in part for the inhibition of DNA synthesis and the S-phase block caused by gossypol. The data also raise the possibility that gossypol may interfere with DNA repair processes as well.

Inhibition of liquefaction and protein degradation in human semen by gossypol

The liquefaction of freshly ejaculated human semen was delayed by gossypol. Liquefaction is normally accompanied by an autolytic degradation of semen proteins, and prior incubation with gossypol can inhibit factors (presumably proteinases) present in seminal plasma that degrade semen proteins. The possible consequences of this inhibition are discussed in relation to the proposed use of gossypol as a vaginal contraceptive.

Mg2+-ATPase activity in the rat testis and its correlation with the stages of spermatogenesis: a histochemical study

The activity of Mg2+-activated ATPase was studied in the rat testis employing histochemical and microphotometrical methods. The enzymatic activity could be correlated with the stages of spermatogenesis. From stage XII onwards, the elongated spermatids showed a weak to moderate activity, which increased from the acrosomal phase to the maturation phase. The reaction product was located in the mid-piece and tail piece of elongated spermatids with a maximum intensity at stage VIII. Morphometric analysis revealed six distinct patterns, which could be correlated with the stages of spermatogenesis.

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.

Inhibition by gossypol of phospholipid-sensitive Ca2+-dependent protein kinase from pig testis

Gossypol, a polyphenolic binaphthalene-dialdehyde extracted from cotton plants which possesses male antifertility action in mammals, is a potent inhibitor of phospholipid-sensitive Ca2+-dependent protein kinase from pig testis. Gossypol inhibited Ca2+-dependent activity of the enzyme without affecting its basal activity. The IC50 value (concentration causing 50% inhibition) was 31 microM when lysine-rich histone was used as substrate. Kinetic analysis indicated that the compound inhibited the enzyme non-competitively with respect to ATP (Ki = 31 microM) or lysine-rich histone (Ki = 30 microM), and competitively with respect to phosphatidylserine (Ki = 2.1 microM). With Ca2+, irrespective of the presence or absence of 1,3-diolein, the compound lowered Vmax and increased the apparent Ka for Ca2+. The compound also inhibited phosphorylation by the enzyme of high-mobility-group 1 protein (one of the endogenous substrates in the testis for the enzyme located in nucleosome), with an IC50 value of 88 microM. These results suggested that a phospholipid-sensitive Ca2+-dependent protein phosphorylation system in the testis is involved in the regulation of spermatogenesis.

Antitumor effects of gossypol on murine tumors

Since the male antifertility drug, gossypol, was shown to be a specific inhibitor of DNA synthesis at moderately low doses in cultured cells, its antitumor potential has been evaluated in three murine tumor models. The effects of gossypol on tumor growth and the survival of 10- to 12-week-old BDF1 mice bearing mouse mammary adenocarcinoma 755 (Ca 755) or P388 or L1210 leukemias, all injected IP, were measured. At an optimum dose of 0.5 mg/mouse given as a single injection at 2 days (48 h) after the inoculation of 10(5) Ca 755 tumor cells, gossypol rendered 66% of the mice free of tumor cells, whereas the remaining 34% died of drug toxicity. The survival rate decreased sharply at doses on either side of the optimum. At suboptimal doses a major proportion of the tumor-bearing mice died of tumor, whereas at higher doses all the animals died of drug toxicity. In other words, the effective dose range of gossypol was rather narrow. The rapidly proliferating mouse leukemias, P388 and L1210, failed to respond to gossypol. Histopathological studies of various organs in the gossypol-treated mice revealed no consistent lesions that could give an indication of organ-specific toxicity of gossypol. The reduction in the myeloid series in the bone marrow of gossypol-treated mice may have been due to depletion rather than direct toxic effect. Further studies are essential to evaluate this compound with regard to its antitumor activity in other murine models.

Gossypol inhibition of adenylate cyclase

Gossypol, a polyphenolic binaphthalene -dialdehyde reputed to exert contraceptive action in males, reversibly inhibits adenylate cyclase [ATP pyrophosphate lyase (cyclizing), EC 4.6.1.1] in a concentration-dependent manner. In membranes prepared from a variety of organs, the half-maximal inhibitory concentration (IC50) ranges from 75 microM (rat Leydig tumor cells) to 250 microM (rat liver membranes). Kinetic studies using partially purified catalytic subunit isolated from bovine testis show that gossypol is competitive with ATP with an apparent Ki of 110 microM. These data suggest that gossypol inhibition of adenylate cyclase is due to direct interaction at the nucleotide-binding domain of the catalytic subunit of the enzyme.

Gossypol induces DNA strand breaks in human fibroblasts and sister chromatid exchanges in human lymphocytes in vitro

The male contraceptive agent gossypol was found to induce a dose related increase of DNA strand breaks in human fibroblasts in vitro at concentrations of 5 to 40 micrograms/ml. The effect was reduced in the presence of 2% fetal calf serum. A weak but reproducible increase in the SCE frequency was found in human lymphocytes treated for 1 hour in serum-free medium with 0.04 to 4 micrograms/ml of gossypol.

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.

Kinetics of gossypol inhibition of bovine lactate dehydrogenase X

Gossypol, a polyphenolic binaphthalene dialdehyde isolated from cotton meal is a potent inhibitor of lactate dehydrogenase-X purified from bovine testis. For the conversion of pyruvate to lactate the IC50 for gossypol is 200 microM for the reverse reaction the IC50 is 12 microM. Gossypol is a competitive inhibitor of NADH, Ki = 30 microM (Km = 17 microM), and NAD+, Ki = 6 microM (Km = 130 microM), and noncompetitive for pyruvate, Ki = 220 microM (Km = 224 microM), and lactate, Ki = 52 microM (Km = 5.6 mM).

Studies on the male antifertility agent--gossypol acetic acid. V. Effect of gossypol acetic acid on the fertility of male rats

Gossypol acetic acid was given to male rats at a dose of 7.5 mg/rat/day six days a week for ten weeks. After nine weeks of gossypol treatment no implantation sites were observed in the females mated with gossypol treated males. After ten weeks of gossypol treatment all the spermatozoa in the vas deferens were non-motile. Gossypol treatment did not affect the body weight and the weights of the accessory sex organs. Plasma LH and FSH levels, hCG binding in testis and succinic dehydrogenase (SDH) and adenosine triphosphatase (ATPase) activities in liver, kidney and testis were not affected by gossypol treatment. Histological observations of the testis revealed partial damage to the seminiferous tubules. Single high doses of gossypol did not induce significant changes in the body weight and weights of testis and accessory sex organs. ATPase activity in the testis was reduced significantly after gossypol treatment, the enzyme activity in liver and kidney, was however, affected at high doses only. Gossypol treatment had no effect on the histoarchitecture of the testis. Intratesticular administration of gossypol evoked localized damage in the testis. Gossypol treatment had no effect on I125 FSH binding to the rat testis homogenate in vitro.

Antifertility efficacy of gossypol acetic acid in male rats

Fertility response and sperm motility of male Wistar rats exposed to various concentrations (2.5 - 30 mg / kg / day) of gossypol acetic acid (GAA) was studied. GAA was given orally. A marked reduction in fertility occurred when rats received more than 15 mg / kg / day of GAA for 5 - 10 weeks (p less than 0.01); dosage below 15 mg had no antifertility effect even after 20 weeks. There is some evidence that GAA administration (30 mg / kg) every other day for 10 weeks had no antifertility effect. A clear relationship between the inhibition of sperm motility and GAA administration was observed (p less than 0.01). The interrelationships between fertility, sperm motility and GAA treatment were analyzed by Yates' chi-square test and Fisher's exact test.