Relaxin as a Regulator of Porcine Granulosa Cell Steroidogenesis and Proliferation

The influence of relaxin (RLX; 0.001 to 1.0 µg ml-1) on the ovarian steroid secretion and proliferation of granulosa cells (GCs) cultured for 48 and 72 h was studied in the presence or absence of gonadotropins. RLX increased ovarian steroid release in a dose dependent manner, but even the highest dose used (1.0 µg ml-1) had no effect on steroid secretion. FSH increased the RLX stimulated steroid release with the exception of the highest dose used. LH in the presence of RLX showed lower effect on GCs steroid secretion. The highest dose of RLX added to the serum free medium in presence of FSH enhanced the (3H)-thymidine labelling of GCs. These results, together with the reports by others demonstrating that RLX is produced by porcine GCs, suggest the intraovarian effect of RLX on granulosa cell functions and show that this polypeptide hormone probably acts indirectly to promote follicle growth and steroidogenesis.