The influence of embryonic tissue homogenate infused into the uterus, on the life-span of the corpus luteum in the sheep.

Abstract

Summary. Following the daily intra-uterine infusion of a homogenate prepared from frozen and thawed tissue of 14- or 15-day sheep embryos the length of the oestrous cycle was significantly prolonged. A single intra-uterine infusion, however, had only a slight effect on oestrous cycle length. The substance derived from the embryonic tissue, which presumably must be of a chemical nature, probably acts on the endometrium in an `anti-luteolytic' manner, that is by counteracting the action of the endometrium which otherwise would have resulted in the regression of the corpus luteum. Unlike homogenate prepared from 14- or 15-day sheep embryos similar material obtained from 25-day sheep embryos did not increase cycle length. This indicates that the effect is dependent on the stage of development of the embryo in relation to the uterus. Homogenate prepared from 14-day pig embryos infused into sheep uteri was unable to maintain the corpus luteum, which suggests that the embryonic factor may be species-specific. Repeated intra-uterine infusions of control material consisting of frozen and thawed saline, serum or serum plus white blood cells had no effect on cycle length. Transfer into the sheep uterus of a whole but heat-inactivated 12-14days sheep embryo had no effect on the cycle length.