RNA SYNTHESIS IN RAT LIVER AFTER CORTISOL TREATMENT: A POSSIBLE MITOCHONDRIAL-NUCLEAR RELATIONSHIP

Abstract

ABSTRACT Liver mitochondrial RNA synthesis (as measured by an RNA polymerase assay) in adrenalectomized ovariectomized rats increased (42 %) 1 h after injection of 0.5 mg cortisol/100 g b. wt. Nuclear RNA synthesis increased (130–171 %) 4 h after injection of 4 mg cortisol/100 g but did not increase after treatment with the lower dosage of cortisol after 4 h. There was no effect on the nuclei from either 0.5 or 4 mg cortisol after 1 h. If either ethidium bromide, rifampicin or actinomycin D were injected 10 min before the hormone injection, a complete inhibition of the hormonal action on mitochondrial RNA synthesis was found. On the other hand, nuclear RNA synthesis was partly inhibited if either ethidium bromide or rifampicin preceded the hormone injection. Actinomycin D inhibited nuclear RNA polymerase below the saline control level. Assuming that ethidium bromide and rifampicin act specifically on mitochondrial RNA synthesis, it would appear that there is a mitochondrial component to the RNA synthesis measured in the nucleus after cortisol treatment.