Triiodothyronine Production by Isolated Rat Hepatocytes: Characterization and Lack of Glucoregulatory Hormone Effects

Summary

Triiodothyronine (T₃) production from thyroxine (T₄) was studied in isolated rat hepatocytes. With an initial T₄ concentration of 0.56 μM, hepatocyte T₃ production was 0.029 ± 0.003 (SEM) pmoles/min/mg protein. T₃ production was greater in hepatocytes than in homogenates from the same liver prepared either before or after liver perfusion with collagenase. Most T₃ produced remained within the cells under the conditions employed. Hepatocyte T₃ production was dependent on cell number, medium bovine serum albumin concentration and temperature. It was stimulated by dithiothreitol, and inhibited by propylthiouracil, 3,3′,5′-triiodothyronine and dinitrophenol; glutathione and ouabain had no effect. Alterations in medium glucose concentration and exposure to insulin or glucagon at several glucose concentrations in vitro did not alter T₃ production. These results indicate that in hepatic tissue T₃ production is enhanced when intact cellular organization is present and that insulin and glucagon do not acutely influence cell production of T₃ in vitro.

Key-Words:

T₃ Production - Hepatocytes - Glucose - Insulin - Glucagon