Variations in some molecular events during the early phases of the reuber H 35 hepatoma cell cycle. I. Glucocorticoid induction of tyrosine aminotransferase.
1. Reuber H 35 hepatoma cell cultures were syncrhonized by serum depletion of the growth medium for 72 hr, which results in arrest of the cells in the G0 or G1 phase of the cell cycle. 2. Induction of tyrosine aminotransferase by dexamethasone was studied. Induction along the cell cycle varies with respect to the sensitivity of the cell towards low hormone concentration and the maximum effect elicited by the hormone. 3. Scatchard analyses of receptor- [3H]triamcinolone binding was performed in cell extracts prepared from cells at various times of G1 and S. Variations were observed in the concentration of glucocorticoid receptor as well as in the affinity of the receptor for the hormone. 4. During the latter part of the cell cycle, variations in the concentrations of the receptor could not explain the variation in enzyme induction, since the maximum rate of induction decreased while an increase in receptor activity still occurred.
D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D004790:Enzyme Induction; D007399:Interphase / Q000187:drug effects; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D051381:Rats; D011987:Receptors, Steroid / Q000378:metabolism; D014221:Triamcinolone / Q000378:metabolism; D014444:Tyrosine Transaminase / Q000096:biosynthesis*
D011987:Receptors, Steroid; D014221:Triamcinolone; D003907:Dexamethasone; D014444:Tyrosine Transaminase