Ovarian steroids in the uterine lumena. I. Effect of LH injection and mating in rabbits

Abstract

Estrogen (E) and progestin (P) were determined in the uterine flushings, esophageal flushings, and peripheral plasma in rabbits at 0 (control), 1, 2, 4, 12, 24, 72 and 168 h after LH (10 μg/kg) injection or after mating. In general, significant quantities of E and P were found in the uterine flushings and in the peripheral plasma. In contrast, esophageal flushings contained significantly lower concentrations of P than that found in the uterine flushings, while E was nondetectable. The effects of mating or LH injection on the content of steroids in the lumen of the uterus were very similar. Two h after the administration of either 0, 1, 10 or 100 μg/kg of LH, the total P content (ng/ml) in the uterine flushings were 0.6, 1, 2 and 3; the total E contents were nondetectable. Progestin concentrations (ng/ml) in plasma removed from the abdominal vena cava for the above treatments were 5, 7, 45 and 38; E concentrations (pg/ml) were 42, 60, 21 and 65, respectively. Ovariectomy 2 h before LH injection resulted in no increase of P and E in the uterine lumen 1 h after LH. It was concluded that LH or mating induces a rapid transport of E and P into the lumen of the uterus and that the release of E and P into the lumen of the uterus requires the presence of the ovaries. The content of lumenal steroid increases until the time of implantation and different E:P ratios are observed at various times after LH or mating. From our results it appears that the ovarian steroids are present in the uterus at critical times of the gamete physiology and implantation.