Postnatal changes in kidney glucocorticoid receptor of mice

The specific binding of [3H]dexamethasone to its receptor and the activation of the hormone-receptor complexes from the kidney of mice at various postnatal ages were investigated. The results indicated that the level (fmol/mg protein) of glucocorticoid receptors remained unaltered at 10-, 15- and 30-day, increased significantly at 45-day and thereafter declined to its earlier level in 60-day old mice. Scatchard analysis of binding data confirmed the increased level of receptors at 45-day compared to day 15, without any change in the hormone affinity to its receptor at these two ages. The extent of temperature- and salt-dependent activation of the receptor showed no marked differences in 10- and 60-day old mice, as determined by DNA-cellulose binding assays. However, the nuclear binding of temperature- and salt-activated glucocorticoid-receptor complexes was significantly higher in 10-day old mice. Cross-mixing experiments showed nuclear specificity in higher binding of thermally activated receptor at day 10 of postnatal age. Molybdate, tungstate and N-ethylmaleimide inhibited the temperature- and salt-dependent activation of glucocorticoid-receptor complexes similarly at both the ages studied. DNase I extraction of bound hormone-receptor complexes from nuclei showed higher extractability at day 10 (63%) compared to day 60 (43%). These findings indicated changes in glucocorticoid receptor concentration together with chromatin organization that might play an important role in glucocorticoid-mediated responses during postnatal development of mice.