Maintenance of the Corpus Luteum of Early Pregnancy in the Ewe. I. Luteotropic Properties of Embryonic Homogenates

Abstract

Experiments were carried out to examine the Iuteotropic properties of embryonic homogenates in ewes. Homogenates prepared from embryos collected 14-15 days postcoitum were infused into the uterine lumen of cycling ewes (n = 4) from Days 12 through 18 postestrus. Four control ewes received isotonic saline only. Embryonic homogenate, infused at a rate of 3 embryonic equivalents/24 h, prolonged the lifespan of corpora lutea through Day 18 postestrus. Mean serum progesterone levels on Days 16, 17 and 18 were 2.2 ± 0.5 ng/ml (±SEM), 2.0 ± 0.4 ng/ml and 1.6 ± 0.4 ng/ml in the treatment group and 0.33 ± 0.29 ng/ml 0.04 ± 0.01 ng/ml and 0.06 ± 0.01 ng/mI in the control group. Luteal weights on Day 18 were 626 ± 22 mg in the treatment group and 194 ± 46 mg in the control group. To determine if the luteotropic property of embryonic homogenate was due to the presence of Ll-I or prolactin-like molecules, we examined embryonic protein in sensitive radioreceptor assays for these hormones. However, 100 pg of embryonic protein had no activity in either the LH-hCG or prolactin radioreceptor assay. In a second study, 100 pg of embryonic protein had no effect on synthesis of progesterone or cAMP in dispersed ovine luteal cells, either alone or in combination with LH and/or prolactin. Synthesis of both progesterone and cAMP could be stimulated in these cells by NIH-LH-S19. The data indicate that homogenates of 14-15-day-old embryos are capable of prolonging luteal function when infused into the uterine lumen, but the effect does not appear to be exerted via an LH or prolactin-like molecule.