Specific receptors for thyroxine in nuclear non-histone proteins of rat thymus during early, medium and late period of life.
Specific binding of 125I-thyroxine to thymus nuclear non-histone proteins of rats aged 7, 14, 45, 80 and 365 days was studied. In 0.4 mol l-1 NaCl nuclear extract of thymocytes practically the same values of Ka were found in rats aged 7, 14, 45 and 80 days (5.72 +/- 0.11 X 10(9) l mol-1, 3.44 +/- 1.65 X 10(9) l mol-1, 5.00 +/- 1.09 X 10(9) l mol-1 and 5.55 +/- 0.95 X 10(9) l mol-1, respectively). As compared to groups of animals of 7, 45 and 80 days of age a marked diminution of Ka (= 1.30 +/- 0.25 X 10(9) l mol-1) with P less than 0.001, less than 0.02 and less than 0.01, respectively, was found in rats aged 365 days. The highest value representing maximum binding capacity (MBC) of 125I-thyroxine was noted in rats aged 45 days (MBC = 6.16 +/- 0.58 X 10(10) molecules per mg of protein) and in adult rats (80 days old) (MBC = 5.82 +/- 1.28 X 10(10) molecules mg-1). In rats aged 7 days a lower value for MBC (= 1.92 +/- 0.77 X 10(10) molecules mg-1; P less than 0.01) was observed as compared to the animals aged 45 days (see above). Similar decrease was found also in old rats aged 365 days (MBC = 3.46 +/- 0.69 X 10(10) molecules mg-1; P less than 0.02). The data quantify the affinity and the specific 125I-thyroxine binding capacity in nuclear non-histone proteins of rat thymus during early, adult and late period of life.
D000375:Aging; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D008297:Male; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone; D013950:Thymus Gland / Q000378:metabolism*
D002868:Chromosomal Proteins, Non-Histone; D011956:Receptors, Cell Surface; D011988:Receptors, Thyroid Hormone