Competition by various steroids for binding of [3H]17,20β-P to ovarian plasma membranes. Ovarian membrane preparations were incubated for 30 minutes with [3H]-17,20β-P in the presence of 10 pM – 10 μM competitor. For explanation of abbreviations see Materials and Methods. Each point represents the mean of triplicate determinations. A) progestogens. B) androgens and estrogen. C) corticosteroids. D) xenobiotics.