GLUTAMINE INCREASES ARGININOSUCCINATE SYNTHETASE MESSENGER-RNA LEVELSIN RAT HEPATOCYTES - THE INVOLVEMENT OF CELL SWELLING

Glutamine, one of the most efficient substrates in the urea cycle, was found to induce the accumulation of argininosuccinate synthetase (ASS ) mRNA in primary cultured rat hepatocytes. The inducing action of glu tamine was obtained at various stages of development and a half-maxima l effect was observed at about 3 mM glutamine. This effect was apparen t from 6 h and persisted for at least 48 h. NH4Cl addition up to 5 mM did not significantly change the ASS mRNA level. Like glutamine, hypoo smotic medium and aminoisobutyric acid (conditions known to increase c ell volume) also increased the ASS mRNA level, which was, in contrast, decreased by hyperosmotic medium. These results demonstrate that the glutamine-induced swelling may participate in the observed increase of the ASS mRNA level. This increase in the ASS mRNA level was associate d with an increase in ASS activity.