Distinct expression of endothelin receptor subtypes A and B in luteinized human granulosa cells

Endothelins (ET) are potent vasoconstrictive peptides originally isolated f rom vascular endothelial cells. Their biological effects are mediated throu gh two different receptors, the endothelin-1 (ET-1)-selective endothelin re ceptor subtype ETA and the non-selective receptor subtype ETB. ET-1 protein has been found in human ovarian follicular fluid and ET-1 mRNA expression has been demonstrated in ovarian tissue. These findings indicate that the e ndothelin-system participates in the modulation of ovarian function, probab ly acting in an autocrine/paracrine manner. In the current study we used fr eshly aspirated, luteinized human granulosa cells (hGC) representing an in vitro model of the early corpus luteum. By means of RT-PCR and immunocytoch emistry we investigated whether luteinized human granulosa cells express ET A and ETB receptors. Specific amplification products of ETA transcripts wer e detected in all samples investigated. In contrast, only after using a thr ee-fold amount of ETB reverse transcripts we were able to demonstrate speci fic, but weak amplification products. In addition, immunocytochemical stain ing for ETA but not for ETB was found in granulosa cell preparations. The p resent study provides clear evidence that human granulosa cells predominant ly express ETA receptor subtype mRNA and protein hinting to its possible ro le in follicle maturation and corpus luteum formation.