Endothelin B receptor is not required but necessary for finite regulation of ovulation

AIMS:In the ovary, endothelins regulate a variety of ovarian functions that include but not limited to folliculogenesis, steroidogenesis, oocyte maturation, ovulation and corpus luteum (CL) function. Two cognate receptors, EDNRA and EDNRB are constitutively expressed in the ovary, and mediate the regulatory endothelin actions. However, the physiological significance of the presence of the two receptors that often elicit opposite responses upon activation by an endothelin is yet to be determined. This study was proposed to test the hypothesis that both receptors are present in the ovary to lend an endothelin a finite regulation of ovulation. MAIN METHODS:A rescued EDNRB knockout (rEDNRB-KO) mouse that is deficient of EDNRB expression in all cells but adrenergic cell lineage was used to test the impact of the loss of function of EDNRB on ovulation. The EDNRB gene deletion and its confirmation at mRNA level were assessed by molecular biology techniques, and the number and size of corpus lutea was determined by ovarian histology. KEY FINDINGS:Female rEDNRB-KO mice had larger litter sizes (numbers of pups per birth) and their ovaries contained more corpora lutea than wild type littermates. SIGNIFICANCE:This result shows that without EDNRB excessive ovulation occurs, suggesting a role of EDNRB in having the extent of ovulation confined.