Specificity of binding to cytosolic proteins in male rat liver cytosol. Two hundred microliters of male rat liver cytosol were incubated with 1.5 nM [3H]R1881 in the absence (control, 100%) and presence of 1-, 10-, 100-, and 1000-fold excess of potentially competing drugs or hormones. , control = 100%; ●-●, [3H]R1881; ▲-▲, 5 α-dihydrotestosterone; △-△, spironolactone (SPIRO); ○-○, potassium canrenoate (K-CAN).