THE EFFECT OF OESTROGENS ALONE OR IN ASSOCIATION WITH PROGESTAGENS ON THE FORMATION AND REGRESSION OF THE CORPUS LUTEUM OF THE CYCLIC COW

Abstract

estrogens show a variety of effects on the mammalian corpus luteum, depending on the stage of the oestrous cycle at which they are administered. This report discusses an investigation of the effect of a single injection of either mg oestradiol benzoate or 5 mg oestradiol valerate, at all stages of the cycle in the cyclic cow. The concentration of plasma progesterone in daily peripheral blood samples, the apparition of oestrus and the occurrence of ovulation and pregnancy were the criteria used to evaluate the effects on the corpus luteum. A multiplicity of effects was the result : luteotrophic, or antiluteotrophic at the beginning of the cycle, luteolytic during most of the luteal phase, and anti-luteolytic at the end of the luteal phase.