[Binding of glucocorticoid hormones and cholesterol to rat brain and liver mitochondria]

The binding of four [3H]glucocorticoids and [3H]cholesterol to rat brain and liver mitochondria in vitro was studied. The binding was the most intensive in the case of steroids having a higher hydrophobicity of the molecule. The binding of [3H]glucocorticoids was decreased by simultaneous addition of [14C]cholesterol, whereas cholesterol binding to mitochondria was stimulated by glucocorticoids. Rotenone as a hydrophobic compound also acted competitively on the binding of glucocorticoids and cholesterol. The binding or all the steroids under study was very fast, reaching the plateau within 5 minutes. After destruction of the outer membrane by hypotonic treatment of a freezing -- thawing procedure the liver mitochondria bound more cholesterol but fewer glucocorticoids than the intact ones. The hydrophobic type of glucocorticoid binding to endogenous cholesterol or phospholipids in the outer mitochondrial membrane and a resulting lack of any specific receptors for glucocorticoids in the mitochondria were postulated. The effects of glucocorticoids on oxidative metabolism in mitochondria are presumably of membraneous nature. Mitochondria can also be considered as a target for glucocorticoid action.