BINDING OF HORMONES AND RELATED COMPOUNDS BY NORMAL AND CHOLESTEROL-DEPLETED PLASMA MEMBRANES OF RAT LIVER

The effects of removing part of the unesterified cholesterol from rat liver plasma membranes upon their ability to bind a number of different hormones and related compounds has been studied. Amongst steroids, the more polar compounds containing an 11 βOH group (dexa-methasone, cortisol, corticosterone) are bound to a greater extent by cholesterol-depleted membranes than by control membranes whilst the less polar compounds (deoxy-corticosterone, progesterone, testosterone, diethylstilboestrol) are bound to a lesser extent. The increase in binding of cortisol is related to the degree of cholesterol depletion. In comparison experiments using rat liver mitochondrial preparations, which normally possess a very low level of cholesterol, it is found that when this level is raised, the binding of corticosterone decreases and that of testosterone increases. Binding of adrenaline and thyroxine by cholesterol-depleted plasma membranes is greater than that of controls whereas the binding of peptide hormones (insulin, glucagon, oxytocin, vasopressin) is much lower. The results suggest that membrane sterols play an important part in regulating the uptake of biologically active compounds. © 1969.