Effect of prostaglandin F-2 on steroidogenesis by porcine corpora lutea

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Abstract
The relationship between luteal cholesterol bound to cytochrome P450scc enzyme and progesterone [P] production was studied in the pig. Luteal P peaked on day 10 of the estrous cycle, declined slowly until day 13 and then precipitously from days 13-14. The P450scc was nearly saturated with cholesterol from days 4-13, but changed abruptly by day 14 to a partly depleted state which persisted until day 16. Total P450scc did not decline significantly until day 17. There was no change in cholesterol esterase activity in a 105,000 g supernatant or in total mitochondrial cholesterol during this period. I.v. administration of prostaglandin [PG]F2.alpha. to hysterectomized gilts resulted in a rapid depletion of cholesterol from P450scc with a half-life of about 2 h. The new level of cholesterol-P450scc interaction (less than 45% of cytochrome) persisted for at least 36 h after treatment. This was paralleled by declines in plasma and luteal P. PGF2.alpha. provokes a decline in P secretion around day 13 by first decreasing the supply of cholesterol to P450scc.