Amino acid transport in isolated hepatocytes: effect of glucagon.
Amino acid transport was studied in freshly isolated adult rat hepatocytes using non-metabolizable alpha-amino-1-[14C] isobutyric acid and 1-aminocyclopentane-1-[14C] carboxylic acid. In the presence of sodium, hepatocytes concentrated alpha-aminoisobutyric acid; this concentrative component of the transport had properties similar  to transport system A. The sodium-independent transport of aminocyclopentane carboxylic acid had properties similar to transport system L (facilitated diffusion). Glucagon stimulated the influx of alpha-aminoisobutyric acid into hepatocytes. The glucagon effect (a) occurred rapidly, but its full expression required two hours of exposure of the cells to hormone; (b) involved new protein (and possibly RNA) synthesis; and (c) occurred at low concentrations of glucagon (50% effect with 0.4 nm). Glucagon stimulated only system A. Cyclic AMP also stimulated the transport of alpha-aminoisobutyric acid. Freshly isolated hepatocytes appear conveniently suited to the investigation of various aspects of the regulation of liver amino acid transport in normal and pathophysiological states.
D000596:Amino Acids / Q000378:metabolism*; D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003515:Cycloleucine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005934:Glucagon / Q000494:pharmacology*; D006854:Hydrocortisone / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008115:Liver Regeneration; D008297:Male; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects; D012964:Sodium / Q000494:pharmacology
D000596:Amino Acids; D000621:Aminoisobutyric Acids; D011956:Receptors, Cell Surface; D003515:Cycloleucine; D005934:Glucagon; D003513:Cycloheximide; D012964:Sodium; D000242:Cyclic AMP; D006854:Hydrocortisone