Cyclical changes in the uterine endometrium and peripheral plasma concentrations of progesterone in the marsupial Trichosurus vulepcula

Abstract

The proliferation and secretory activity of the uterine endometrium in the marsupial T. vulpecula is examined at the cellular and subcellular levels throughout the 26-day oestrous cycle. The observations described are correlated with measured concentrations of progesterone in the peripheral blood plasma. Evidence cited indicates that there are no significant functional differences in the uterine endometrial secretory activity during the 17.5-day gestation period in pregnant females, compared with those in a normal oestrous cycle. Progesterone assays carried out on blood plasma taken from 20 staged animals throughout the oestrous cycle, five of which were at known stages of gestation, also supports the view that pregnancy does not significantly alter the physiological pattern of the reproductive cycle in this marsupial.