THYROID-HORMONE ACTION IN PORCINE LUTEAL CELLS - EFFECT OF TRIIODOTHYRONINE ON MITOCHONDRIAL CYTOCHROME P450(SCC) ACTIVITY

In the present study hydroxylated cholesterol derivatives were used to monitor P450(scc) activity as an effect of triiodothyronine. Luteal c ells isolated from mid-developing and mature corpora lutea were plated into 24-well plates by 18 h incubation with M199 supplemented with 5% of alf serum. After that time the plates were washed with fresh M199 and hydroxylated cholesterol derivatives (25-, 20-, and 22-hydroxylate d cholesterol) were added to the control (not-T3-treated) and T3-treat ed cells. Two hours later, all cultures were terminated and the media were frozen until further progesterone analysis. Triiodotyronine added to the culture medium of cells isolated from mature corpora lutea inc reased both basal and hydroxylated cholesterol derivative-stimulated c ells. Aminoglutethimide, a P450(scc) enzyme inhibitor, added to the cu lture medium in all doses used, had no effect on basal progesterone se cretion while added to the T3-treated cells reduced progesterone produ ction. This study strongly supports the hypothesis of a direct effect of thyroid hormone on mitochondrial cytochrome P450(scc) - catalysing side-chain cleavage of cholesterol enzyme in luteal cells.