A Na(+)-dependent system A and ASC-independent amino acid transport system stimulated by glucagon in rat hepatocytes.

Abstract The effects of glucagonon amino acid transportin rat hepatocytes are not fully understood. We examined the effect of this hormone on alanine, serine and cysteinepreferring system (system ASC)-mediated amino acid transportin rat hepatocyte monolayers using 2-aminoisobutyric acid(AIB) and l - cysteine. Glucagoninduced a time and protein synthesis-dependent stimulation of Na + -dependent alaninepreferring system (system A)-independent AIB transport. The glucagon-induced increase in transport activity was not modified by substrate starvation and not related to changes in the intracellular pool of amino acids. Glucagondid not modify system ASC activity measured by l - cysteine. Therefore the transport activity of AIB independent of system A stimulated by glucagoncannot be attributed to system ASC. This suggests a Na + -dependent transport system in rat hepatocytes not identified until now.