Exfoliative Cytology in Vaginal Vestibule of Female Asian Elephants: Relation to Circulating Progesterone Concentrations

Abstract The estrous cycle of the Asian elephant (Elephas maximus) was monitored by analysis of exfoliative cytology in the vaginal vestibule and serum progesterone concentrations. Appearance frequency of each 5 exfoliative cells; parabasal, intermediate, superficial anuclear and nuclear cells and leukocytes; on the smear collected from two elephants was calculated, and serum progesterone concentrations were measured by radioimmunoassay. Serum progesterone concentrations changed regularly with the cycle between 14 and 17 weeks. Using spectrum analysis (Yule-Walker method) to appearance frequency of exfoliative cells, it was found that the time when a superficial cell markedly appeared in vaginal vestibule corresponded to the time when serum progesterone concentration was almost negligible. It is suggested that the time when numbers of two kinds of superficial (anuclear and nuclear) cells and parabasal and intermediate cells increase to the smear of the elephant, means the period from proestrus to estrus a...