Changes in cortisol binding to soluble receptor proteins in rat liver and thymus during development and ageing.

Changes in labeled cortisol binding to soluble cytoplasmic proteins of rat liver and thymus during development and ageing of animals have been observed.The relationship of age and cortisol binding to a fraction of soluble liver proteins precipitated at 50% saturation with ammonium sulfate displayed two maxima: The first one on the seventh day of postnatal life and the second one at 2.5 months of age. Binding of hormone to macromolecules of the same fraction prepared from older animals was less efficient. Almost the same picture has been obtained when total bound activity to macromolecular cytosol fraction was expressed per milligram of dry weight of liver.Binding of labeled cortisol to total cytosol macromolecules of liver and thymus was most efficient in 3-month-old animals and decreased after that, which is of interest in view of totally opposite effects of glucocorticoids upon various biosynthetic processes of these organs.