Sex Hormonal Pattern of the Female African Giant Rat (Cricetomys gambianus, Waterhouse) at Different Stages of the Oestrous Cycle

Enzymeimmunoassay (EIA) system was used to measure the serum concentrations of follicle stimulating hormone (FSH), luteinising hormone (LH), estrogen, progesterone and prolactin in a total of thirty-five sexually matured female African giant rats (cricetomys gambianus, Waterhouse) at different stages of the oestrous cycle in order determine sex hormonal pattern. Exfoliative cytology of vaginal smears was used to classify the rats into different phases of the oestrous cycle. The results showed lack of LH surge at late proestrus/early estrus when estrogen had highest serum concentration of 88.7 ± 0.14ng/ml and, estrogen and progesterone had inversely related cyclic pattern. Progesterone serum concentration (96.8 ± 11.21ng/ml) was significantly high (p<0.05) at late metestrus/early diestrus but was at its basal level at late diestrus/early estrus. Prolactin serum concentration (20.7 ± 2.92ng/ml) decreased significantly (p>0.05) at late diestrus/early proestrus and was at its peak during mid estrus. Prolactin serum concentration displayed inverse relationship with the FSH whereas it exhibited synergism with estrogen serum concentration. The hormonal pattern suggested that probably ovulation occured at late diestrus/early proestrus and perhaps female African giant rat was a spontaneous ovulator. KEY WORDS: African giant rat, Oestrous cycle, Sex hormones