Triiodothyronine-stimulated RNA synthesis in primary cultures of adult rat hepatocytes

Abstract

We have studied the effect of triiodothyronine (T 3) on RNA synthesis by primary cultures of rat hepatocytes in order to ascertain whether hepatocyte transcriptional activity is directly stimulated by this hormone. The results demonstrate that T 3 stimulates RNA synthesis as measured by [ 3H]orotic acid incorporation into RNA and by RNA polymerase activity. The responsiveness of cultured hepatocytes to T 3 becomes evident only after a fairly long latency period required for the recovery of T 3 nuclear binding sites. The response of RNA synthesis to T 3 was absent unless the hepatocytes were simultaneously exposed to insulin and dexamethasone, indicating a permissive role of these factors in the action of T 3 on RNA synthesis.