Uptake of cortisol in vitro by rat liver mitochondria

¹ Department of Physiology, Yale University School of Medicine, New Haven, Connecticut

The uptake of cortisol by isolated rat liver mitochondria was studied with the aid of the C¹⁴-labeled hormone. Evidence is presented which indicates that the hormone enters the mitochondria by diffusion and that the process is extremely rapid. Following incubation, 95% of the cortisol and its metabolites could be removed from the mitochondria by two washings with 0.25 m sucrose. Although submitochondrial particles prepared by disrupting mitochondria either sonically or with desoxycholic acid also accumulated cortisol-4-C¹⁴, the uptake was considerably less than that of intact mitochondria. Radioautograms of chromatographed mitochondrial extracts showed that mitochondria metabolized cortisol primarily to compounds more polar than cortisol and that this process was inhibited by 2,4-dinitrophenol and sodium cyanide but not by p-chloromercuribenzoate.