Endothelin-1 is an autocrine/paracrine regulator of porcine granulosa cells.

We studied whether a novel vasoconstrictor, endothelin-1 (ET-1), is synthesized by and released from porcine granulosa cells, and whether ET-1 acts directly on granulosa cells in an autocrine/paracrine fashion. The dilution curve of the conditioned medium from cultured porcine granulosa cells was parallel to a standard curve of ET-1 in RIA. Reverse-phase HPLC of the conditioned media from the granulosa cells revealed a major peak of ET-1-like immunoreactivity (ET-1-LI) coeluting with standard ET-1. ET-1-LI was released from cultured porcine granulosa cells as a function of time. Northern blot analysis demonstrated the expression of mRNA for prepro-ET-1 in the granulosa cells. We demonstrated the presence of ET-1 in the follicular fluid of porcine ovaries, and that the concentration of ET-1 in large follicles was higher than that in small-medium follicles. ET-1 dose-dependently stimulated cell growth and DNA synthesis in porcine granulosa cells. ET-1 inhibited the FSH- and hCG stimulated accumulation of progesterone in porcine granulosa cells in long-term incubation. These findings suggest that ET-1 produced by porcine granulosa cells may function as an autocrine/paracrine growth factor and modulator of steroidogenesis in ovarian granulosa cells.