[Comparative characteristics of cytosol glucocorticoid receptors from normal liver, the liver of tumor-bearing rats and hormone unresponsive Zajdela hepatoma].

Specific dexametasone (D) and cortisol (F) receptors have been found both in liver and Zajdela hepatoma. Rat liver cytosol receptors are characterized by the association constant (Kas) = 3,8 X 10(8) M-1 for D and 0,57 X 10(8) M-1 for F as well as by a number of binding sites (NBS)=4,9 X 10(-13) moles/mg protein and 4,06 X 10(-13) moles/mg protein, respectively. The receptors show stric specificity to glucocorticoids. Cytosol glucocorticoid-receptor complexes from liver and hepatoma sediment at 6-7S, when centrifuged in the buffer of a low ionic strength, and at 3-4S in the buffer of a high ionic strength (0,4 M KCl). The properties of cytosol receptors in the course of in vivo hepatoma growth were found to be gradually altering: Kas for D dropped whereas that for F increased; the NBS is decreased 3-4 fold as compared to normal liver cytosol--which may partially be accounted for by the unresponsiveness of the tumour to the hormones.