Effect of embryo on corpus luteum function.

Abstract

The relationship that exists between the embryo and the corpus luteum is analyzed with particular emphasis on the effects of the embryo on luteal function in early pregnancy. In animals such as the sheep and pig the presence of embryos in the uterus prolongs the life span of the corpora lutea but does not increase their functional capacity. The embryos exert their effect on the corpora lutea during early pregnancy in a local manner which is demonstrated by the fact that unilateral luteal regression can be induced in pregnant sheep and pigs by retaining a segment of 1 uterine horn in a nongravid condition. It is suggested that during early pregnancy in sheep and pigs the embryo acts either by protecting the corpora lutea from the lytic effect of the uterus or by preventing the uterus from acquiring its lytic properties. In the guinea pig rat and mouse the life span and the functional activity of the corpora lutea are increased during pregnancy. The 1st effect of the embryo on luteal function in the sheep is seen on the 12th-13th day after estrus and in the guinea pig 10-14 days after mating. In the Mustelids and Marsupials the embryo appears to have little or no effect on luteal function.