Antifertility Effects of Orally Administration of Low Dose Gossypol Acetic Acid Combined with Methyltestosterone Plus Ethinyl Estradiol on Male Rat

Objective To investigate the feasibility and optimal regimen of orally administration of low dose gossypol acetic acid （GA） combined with methyltestosterone （MT） plus ethinyl estradiol （EE） for contraception in males.Methods Wistar male rats were randomly assigned into four groups, 20 in each group. Animals in group A or B were administered daily with 1% methyl cellulose or GA （12 mg/kg） suspended in 1% methyl cellulose, respectively. Rats in group C or D took firstly GA 12 mg/kg＋MT 20 mg/kg＋EE 0.1 mg/kg or MT 20 mg/kg＋EE 0.1 mg/kg, in asuspension with 1% methyl cellulose, via gastric intubation. After the infertilities were initiated（6 weeks for group C, 8 weeks for group D）, GA was served alone while MT＋EE were withdrawn in rats of groups C and D. The treatment was ceased after 18 weeks and some males from group C were permitted to recover. Fertility testing, 10 males per group, was served for determining infertility or restoration of fertility in treated rats. Examinations of histology and biochemistry in treated rats were used to examine the morphologic influences on sperm, testis, epididymides and viscera, and biochemical changes in blood. The growth and development of F1 generation of the rats would also be tested in a series of behavioral tests.Results Ten rats from group C were infertile at week 6 after treatment, and the fulfilled infertility was maintained with low-dose GA （12 mg/kg） only daily. Six weeks after cessation of treatment, all of treated males recovered their fertility. However, 8 of 10 rats from group D were in sterility at 6th week of treatment and all at 8th week of treatment, but the infertility could not be kept with the similar dose GA alone later on. Moreover, no adverse effects were found in our present experiments.Conclusion Administration of oral low dose GA combined with MT and EE as loading dose could successfully induce infertility in short term, whereafter the efficacy could completely be maintained by similar low dose of GA alone for long term. The combined regimen should be safe, effective, reversible and long term, and then optimal and promised contraception for male.

Inhibition of Acrosomal Enzymes by Gossypol Is Related to Its Antifertility Action

To investigate into the mechanisms underlying the irreversible sterility induced by gossypol, we studied the relationship between its inhibitory action on acrosomal enzymes and its antifertility effect.As shown by our result, after exposure to gossypol (l.25-60 μg/ml) for 15 min. in vitro,the sperms' ability to penetrate bovine cervical mucus and the fertility rate were significantly reduced. Also, following administration of gossypol (12.5 mg/kg/day) for six weeks, the rate of fertilization in vitro by hamster sperm was significantly decreased. In the gossypol-treated group, extracts of testis sperm delayed dispersion of cumulus cells, suggesting inhibition of hyaluronidase and other acrosomal enzymes. Furthermore, the acrosin and arylsulfatase activities were shown to be markedly inhibited. Thus, a parallelism was displayed between the reduction of fertility and the decreasc in acrosin and arylsulfatase activities in epididymis sperms.Besides, the inhibition was reversible and was dosage-and durationdependent. In conclusion, the assay of acrosin activity might serve as a useful tool for monitoring the irreversible sterility induced by gossypol,