Spermicidal activity of Magainins: in vitro and in vivo studies.

ABSTRACT

Spermicidal efficacy of two synthetic antimicrobial peptides, viz. Magainin-A (Mag-A) and Magainin-G (Mag-G), have been studied under in vitro condition using rat and human spermatozoa. The data showed that sperm motility was inhibited with various concentrations of Magainins at different intervals ranging from 20 to 480 seconds as compared to controls. The minimum concentration of Mag-A required to immobilize spermatozoa (40-60 x 10(6)/ml of saline) within 20 seconds was found to be 100 micrograms in rat and 200 micrograms in human. The action of Mags on sperm motility was observed to be dose-dependent. The activity of Mag-A was significantly (P < 0.05) higher than Mag-G (P < 0.05). The in vivo studies in rats indicated that Mag-A when applied intravaginally, on the day of estrus, at the dose level of 200 micrograms, for five consecutive estrous cycles, induced no abnormalities either in the length of estrous cycle or in morphology of vaginal epithelial cells. When Mag-A was applied intravaginally before mating on the proestrusestrus day, complete arrest of sperm motility with 200 micrograms concentration was observed and none of these treated females conceived after the mating. In view of these facts, it is suggested that Mag-A, having anti-bacterial, anti-viral, anti-fungal and spermicidal activities, could be a potent vaginal contraceptive.