Binding of 3H-dexamethasone and 3H-corticosterone to rat liver cytosol during postnatal period

The binding of 3H-dexamethasone (3H-Dx) and 3H-corticosterone (3H-B) to specific binding proteins of rat liver cytosol was compared during the pre- and postnatal period. The binding of 3H-Dx was almost twice as high as that of 3H-B during the whole postnatal period. The Scatchard analysis showed the number of binding sites for 3H-Dx to be 4.4x10-13 mol.mg-1 (Ksub(d) 5.9x10-9 mol.l-1) and for 3H-B to be 2.7x10-13 mol.mg-1 (Ksub(d) 1.6x10-8 mol.l-1). A negative relationship between the binding of 3H-Dx to the rat liver cytosol receptors and the level of plasma corticosterone was found and it was concluded that the number of free receptors is to a certain extent dependent on the level of endogenous corticosterone. It seems, however, that in addition to corticosterone, the undetectability of receptors during a short period after birth may also be due to other factors. (author)