Pregnenolone-Binding Proteins in the Rat Adrenal Cortex

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Abstract
Rat adrenal cortex contains protein(s) that binds pregnenolone with high affinity. This binding, demonstrated by gel filtration and by a dextran-coated charcoal method, was associated with the cytosol and with fractions solubilized by sonication from the mitochondria and microsomes. The binding of pregnenolone was saturable and was inhibited by mercurials and proteolytic enzymes. Pregnenolone-binding was not influenced by the presence of progesterone, deoxycorticosterone, corticosterone or aldosterone, but was inhibited by steroids with a 3.beta.-hydroxy-5-ene structure similar to pregnenolone and by hydroxymethylene steroid and cyanoketone. This protein may be involved in the intracellular transport and retention of pregnenolone within adrenal cortical cells.