[Fluctuations in the level of progesterone in the peripheral blood of nutria during pregnancy].

The fluctuations in the concentrations of progesterone in peripheral blood of three intact coypus and three coypus after natural mating were investigated for the period of four months. Immediately after mating the concentrations of progesterone are low (1.5-2.4 ng.ml-1), the maximum values reach the peak between the 14th and 15th week of gravidity (12.50-20.72 ng.ml-1), whilst there is almost no change in the intact females. On the last days of gravidity the values of progesterone decrease rapidly and they are very low on the day of parturition (1.0-2.5 ng.ml-1). The concentration of progesterone in the blood plasma of intact females in the test period is low (0.09-3.18 ng.ml-1).