A comparison of RNA metabolism in the visual cortex of sighted rats and rats with retinal degeneration

Abstract

The RNA metabolism in the visual cortex of visually stimulated adult blind and sighted rats has been compared. The blind rats belonged to a strain suffering from an inherited retinal dystrophy. This condition renders them blind after the age of 3–4 weeks. There is no gross difference in the metabolic rate of the blind and sighted strains. No significant differences were seen in the RNA, DNA, and protein content per wet weight of the two types of visual cortex but the RNA DNA ratio was significantly lower in the blind animals. Intraventricularly administered ( 14C) orotic acid was incorporated into RNA to a lesser extent in the visual cortex of the blind animals. This could not be wholly attributed to a difference in the size of the acid soluble pool. Chromatographic studies on RNA hydrolysates and the acid soluble precursor pool indicated that the reduced labeling of RNA in the blind visual cortex was not due to a reduction in the rate of conversion of orotic acid to UTP and thus it would appear that the lowered rate of incorporation of label into RNA is due to a reduced rate of RNA synthesis. This was restricted to the visual cortex, no differences were observed in the frontal cortex. In vitro studies indicated that there were no differences in the total ribonuclease activity in the blind and sighted visual cortex but the RNA polymerase activity (but not the Poly C synthetase activity) was slightly lower in the visual cortex of the blind animals.