Expression of steroidogenic acute regulatory protein and its regulation by interferon-gamma in rat corpus luteum

The steroidogenic acute regulatory protein (StAR) is the key regulatory protein of steroidogenesis. De novo synthesis of StAR protein is required for intramitochondrial translocation of cholesterol to the cytochrome P450 side chain cleavage enzyme which is located on the matrix side of the inner mitochondrial membrane. This is the rate-limiting step of steroid biosynthesis. Using in situ hybridization and immunohistochemistry we studied StAR expression in various stages of the corpora luteal and its regulation by interferon-gamma (IFNγ) in the adult pseudopregnant rat. The results indicated that expression of StAR in the corpora luteal was correlated with progesteron production and IFNγ was capable of inhibiting its expression.