Are human luteinizing granulosa cells a site of action for progesterone and relaxin?

Specific nuclear staining for progesterone receptor (PR) was detected by immunocytochemistry in human granulosa cells (GCs) obtained from in vitro fertilization protocols. The percent of PR-positive cells (60% to 80%) remained unchanged during 7 days of culture in media containing fetal calf serum, in the absence of human chorionic gonadotropin (hCG) or the progesterone antagonist RU486. Progesterone (P) production by GCs cultured on extracellular matrix from bovine corneal endothelial cells was stimulated by hCG and prostaglandin E₂ (PGE₂). However, addition of RU486 or human relaxin had no effect on control, hCG-, or PGE₂-stimulated P production. Thus, the receptor data are consistent with an autocrine action of P in luteinizing GCs, but initial experiments in cell culture did not define a role for P or relaxin in modulating luteal steroidogenesis.