[Progesterone and 17-beta-estradiol concentration in the peripheral blood of pregnant mice at various stages of pre-implantation period of embryonal development].

Radioimmunological method was applied to the study of progesteron and 17 beta-estradiol profiles in the peripheral blood plasma of pregnant mice from the time of the zygote formation (the 1st day of gestation) to the blastocyst implantation (the 5th day of gestation). The peak of a progesteron concentration in the plasma and the onset of reduction in the 17 beta-estradiol concentration were noted in the evening of the 3rd day of pregnancy. From this period there was a fall in the 17 beta-estradiol and progesterone content in the blood plasma. In the evening of the 3rd day of pregnancy the 14-18-cell embryos passed from the oviduct into the uterine cornu. The role played by the embryo in changes of the maternal hormonal status is discussed.