The effect of bovine growth hormone on formation of RNA by rat liver slices

Abstract

1. Rat-liver slices incubated with [ 3H]orotic acid incorporated label into RNA at a linear rate for at least 4 h. Labelled orotic acid was incorporated almost exclusively into 45–55-S RNA during the first 2 h incubation. Ribosomal RNA (18-S and 28-S RNA) as well as soluble RNA became labelled after 4–6 h incubation. 2. Actinomycin D (10 μg/ml) reduced the incorporation of labelled orotic acid into the 45–55-S RNA approx. 75 %. 3. Liver slices from hypophysectomized rats sacrificed 6 or 12 h after bovine growth hormone administration incorporated significantly more label during a 1-h incubation than did slices from untreated animals. Addition of growth hormone directly to the incubation medium had no demonstrable effect on the incorporation of labelled orotic acid into the 45–55-S RNA by liver slices from hypophysectomized rats. 4. Liver slices from hypophysectomized rats sacrificed 12 h after growth hormone administration incorporated approximately five times more label into ribosomal RNA (18 S and 28 S) during a 6-h incubation than did slices from untreated hypophysectomized rats. Growth hormone added directly to the incubation medium did not increase labelled orotic acid incorporation into ribosomal RNA of liver slices.