The effects of postoperative factors on serum thyroid hormones and rat liver nuclear 3,5,3'-triiodothyronine receptor concentrations in surgical models of uremia and regenerating liver.

Abstract

We have determined the individual effects of postoperative fasting, surgical/anesthetic factors, acute uremia (AU), and regenerating liver (RL) on nucleoplasmic (NP; 0.15 M KCl-extractable) and chromatin-bound (CB; 0.4 M KCl-extractable) rat liver T3 receptors. AU and RL rats were studied 24 h after bilateral nephrectomy (blood urea nitrogen, 128 +/- 13 mg/dl) or two thirds hepatectomy, respectively. The effects of postoperative fasting were assessed by comparison of normal rats (N) with control rats (N6) pair-fed to match the caloric intake of the AU and RL rats. Surgical/anesthetic effects were determined by comparison of N6 rats with sham-operated pair-fed rats (S6). The effects of AU or RL were obtained by comparison with S6 controls. Changes in mean body weight attributable to fasting (N6-N), surgical/anesthetic effects (S6-N6), acute uremia (AU-S6), and regenerating liver (RL-S6) were: -17.3 (P less than 0.001), -4.0 (P = NS), -4.5 (P less than 0.05), and -1.0 g/24 h (P = NS), respectively. Changes in mean serum T4 (N, 5.3 +/- 1.3 micrograms/dl) were: -1.0 (P = NS), -0.6 (P = NS), -0.9 (P less than 0.05), and -1.0 micrograms/dl (P less than 0.05), respectively. Changes in mean serum T3 (N, 53 +/- 23 ng/dl) were: -8 (P = NS), -18 (P less than 0.05), -10 (P = NS), and -14 ng/dl (P less than 0.05), respectively. The NP and CB receptor pools of the AU and RL rats were not significantly different from those of age-matched N rats (NP, 25 +/- 5 fmol/mg DNA; CB, 405 +/- 134 fmol/mg DNA). Chronically uremic (CU) rats 2 weeks after five sixths nephrectomy (blood urea nitrogen, 36 +/- 2 mg/dl) did not exhibit significant change in their extractable receptor pools. Complete starvation for 24 h (NO) or 72 h (NOO) generally resulted in marked reductions in receptor concentrations compared to those in age-matched N rats fed ad libitum: NP pool (N, 31 +/- 17 fmol/mg DNA): NO-N, -40% (P = NS); NOO-N, -59% (P less than 0.01); CB pool (N, 303 +/- 105 fmol/mg DNA): NO-N, -19% (P less than 0.05); NOO-N, -41% (P less than 0.001). These studies indicate that severe AU, moderate CU, and LR have relatively little effect on solubilized rat liver nuclear receptor concentrations. In contrast, complete starvation is a potent depressant of both nuclear receptor pools. In the surgical models of AU and LR, postoperative fasting was the primary cause of weight loss.(ABSTRACT TRUNCATED AT 400 WORDS)