Binding parameters of rat liver nuclear receptors for T3 after partial hepatectomy or bilateral adrenalectomy and serum T4 and T3 levels.

Nuclear receptor affinity (Ka) and maximal binding capacity (MBC) for 3,5,3'-triiodothyronine (T3) in rat liver was estimated at 1, 12, 24, 48 and 120 hours after partial hepatectomy and 1, 24, 30, 40 and 120 hours after bilateral adrenalectomy and related to serum T4, T3 levels. Soluble T3 receptor fraction was prepared from purified rat liver nuclei and the values of Ka and MBC were calculated by Scatchard plot analysis from the saturation curves. As compared to sham operated rats a significant diminution in MBC for T3 (P less than 0.05) in the remaining about one third of liver tissue at 12, 24 and 48 hours after partial hepatectomy was observed. The thyroxine (T4) level in serum was diminished (with P ranging from less than 0.001 to less than 0.01) at 12, 24 and 48 hours after partial hepatectomy, while no changes in T3 serum level were found at all indicated time intervals. In contrast, no changes in Ka or MBC for T3 in rat liver nuclear receptor as well as in serum T4 and T3 levels were demonstrated 1, 24, 30, 40 and 120 hours after adrenalectomy. The data reflect an appreciable relation between nuclear receptor occupancy for T3 and serum T4 level after partial hepatectomy, serum T3 level and Ka for T3 of nuclear receptor remaining unchanged.