Enhancement of nucleolar RNA synthesis by chromium (III) in regenerating rat liver.

Rats pretreated with CrCl3 at an intraperitoneal dose of 5 mg Cr/kg body weight, and then subjected to partial hepatectomy concentrated Cr in the regenerating liver cells, especially in the nucleoli. Hepatic RNA synthesis induced by partial hepatectomy was further enhanced by Cr(III) administration without changes of the nucleotide pool size at least for 12 hr after the hepatectomy. Of the RNA species newly synthesized, the synthesis of nucleolar RNA was predominantly enhanced. The nucleolar RNA thus synthesized in the regenerating liver of Cr(III)-dosed rats followed normal processing into rRNA as estimated by actinomycin D-chase experiments followed by sucrose density gradient centrifugation analysis and also by nucleotide composition analysis of nucleolar and ribosomal RNAs. These results suggest that Cr accumulated in nucleoli may participate in nucleolar gene expression.