Effect of melatonin on reproductive indices in untreated females following mating with F1 male Wistar rats exposed in utero and via lactation to mixture of chlorpyrifos and cypermethrin

The study investigated effect of melatonin (MEL) on reproductive indices in untreated females mated with F1 male rats exposed in utero and via lactation to mixture of chlorpyrifos (CPF) and cypermethrin (CYP), and in the resulting F2 male rats. Sixty pregnant dams obtained via overnight mating of 72 nulliparous females with sexually mature males in a 1:1 mating scheme were divided into 6 groups of 10 animals each. Groups I (DW), II (S/oil) and III (MEL) were given distilled water (2 ml/kg), Soya oil (2 ml/kg) and melatonin (0.5 mg/kg) only, respectively, while group IV (CC) was co-administered with CPF (1.9 mg/kg) and CYP (7.5 mg/kg). Group V (MCC) was pretreated with MEL (0.5 mg/kg) and then co-exposed to CPF (1.9 mg/kg) and CYP (7.5 mg/kg), 30 minutes later. Group VI (CCM) was co-exposed to CPF (1.9 mg/kg) and CYP (7.5 mg/kg) and then treated with MEL (0.5 mg/kg) 30 minutes later. The regimens were administered by gavage once daily from gestation day 1 to postnatal day (PND) 21. The dams were allowed to deliver normally and the males F1 generation obtained from them was allowed to mate nulliparous females at PND 80 overnight in a ratio of 1:1 and some reproductive indices were thereafter evaluated. The mated females were evaluated for mating index, fertility index, gestation index and gestational length, while the resulting F2 male rats were evaluated for live birth index, viability index and sex ratio. The results revealed decreased mean gestational length, viability index and sex ratio in the CC group (p<0.05) relative to that of the other groups. Although not significant (p>0.05), the mating, gestation (pregnancy), fertility and live birth indices in the CC group were relatively lower when compared to that of other treated groups. In conclusion, alterations of reproductive indices from mating of nulliparous females with F1 male rats exposed in utero and via lactation to mixture of CPF and CYP were mitigated by melatonin.