ON MECHANISM OF HORMONE ACTION .12. UPTAKE OF 1,2-3H-CORTISOL BY ISOLATED RAT LIVER NUCLEI

Addition of 1,2-3H-cortisol to isolated rat liver nuclei leads to a rapid uptake of the hormone which reaches a plateau after 20 min incubation at 37 °C. The uptake of labelled cortisol by the isolated nuclei has been also confirmed by autoradiography. The incorporation of the hormone into the nuclei is temperature-dependent and can be inhibited by preincubation of the nuclei with unlabelled cortisol and other structurally related steroids, as well as by thiol blocking agents. Almost all the radioactivity incorporated by the nuclei within the first 30 min of incubation at 37 °C with 3H-cortisol is recovered in the form of unchanged cortisol. The retention of cortisol by the nuclei is also temperature-dependent and is decreased by unlabelled hormone as well as by thiol blocking agents. © 1969.