Expression of the genes of arginine-synthesizing enzymes in the rat kidneyduring development

The expression of two genes, coding for argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL), enzymes which synthesize arginine, was s tudied by Northern analysis in various tissues of fetal rats. The highest e xpression of both genes was seen in the small intestine, liver and kidney o f the fetus. The developmental expression was observed in the kidney where both mRNA levels remained low during the fetal period and they increased co ncomitantly in both kidney and liver throughout the perinatal life, suggest ing that the aptitude to synthesize arginine appeared and developed within the same period in both organs. this developmental activation of the ASS an d ASL genes expression corresponded, at least in part, to a transcriptional mechanism in both tissues, as measured by run-on assay. Bilateral adrenale ctomy showed that glucocorticoids did not appear to control the development al expression of both genes in the kidney, in contrast to the situation obs erved in the liver.