Local effect of the rabbit embryo-foetus on uterine progesterone and pregnenolone levels.
Rabbit peripheral serum and uterine tissue (embryonic (EZ) and interembryonic (IEZ) zones) were assayed for the main C21, C19 and C18 steroids throughout pregnancy and pseudopregnancy (PSPG). Pregnenolone concentrations in PSPG and IEZ were comparable and remained relatively stable, while its level in EZ increased, reaching a peak value of 18.2 +/- 0.8 ng/g by day 15, and decreasing thereafter to a level comparable to oestrus by day 25. Tissue concentrations of progesterone were comparable in PSPG and IEZ, reached their maximal level on days 6.5 and 9, and decreased significantly (P less than 0.01) on day 15. In EZ, progesterone level was significantly lower than in IEZ and decreased on day 9 compared to day 6.5. A further decrease was observed from days 9 to 15 but no difference between tissues was observed on the latter day. Thus, the blastocyst-foetus exerts a local effect by decreasing progesterone content and increasing pregnenolone level in the uterine tissue adjacent to its implantation (EZ). The conversion of progesterone in uterine tissue to less-active metabolites does not appear to occur towards the C19 and C18 steroids.
Dugré
F J
FJ
Ontogénie et Reproduction, Sainte-Foy, Québec, Canada.
Lambert
R D
RD
Bélanger
A
A
Fortier
M A
MA
Caron
S
S
D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D004622:Embryo, Mammalian / Q000502:physiology*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D011284:Pregnenolone / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism*; D011555:Pseudopregnancy / Q000378:metabolism; D011817:Rabbits; D014599:Uterus / Q000378:metabolism
D011374:Progesterone; D004958:Estradiol; D011284:Pregnenolone