ASPECTS RELATED TO FORMATION, FUNCTION AND REGRESSION OF SUPPLEMENTARY CORPORA LUTEA IN MARES

Abstract

Supplementary corpora lutea (SCL) are ovarian structures that develop from 36-40 days of gestation through equine chorionic gonadotropin (eCG) hormonal stimulation, secreted by the endometrial cups. The SCL are composed by accessory corpora lutea, resulting from follicle luteinization and by secondary corpora lutea, which arise from some follicles ovulation. These structures, together with the primary corpus luteum and the fetoplacental unit, constitute one of the progesterone sources that contribute to pregnancy maintenance in equine species. The process that gives rise to the supplementary corpora lutea involves endocrine and immunological features, triggered by the origin of the endometrial cups, that in turn secrete eCG stimulating SCL formation. However, the purpose of this invasion and its subsequent immunological response involves pregnancy maintenance mechanisms. Progesterone supplementation by these corpora lutea is limited and regression of these structures is connected to endometrial cups regression, although the latter occurs before the SCL regression. The SCL study allows explanation of the real contribution of these structures to pregnancy maintenance and also enables reduction of hormone treatment applied in embryo transfer programs.