[Effects of experimental hyperammonemia on the secretion of insulin and glucagon in the rat]

In order to investigate the controverted effect of ammonia on insulin and glucagon secretion 3 groups of 55 rats were perfused either by Na+ acetate (controls), either by NH4+ acetate: in the first group plasma insulin (IRI) and glucagon (IRG) levels were compared before and after perfusion; the second group was supplemented by glucose perfusion (1 g/100 g/hour); in the last group an arginine perfusion (1 g/kg/min) was started 15 min after the beginning of NH4+ or Na acetate and IRI and IRG levels were determined in the portal blood. Hyperammonemia, which reached about 500 microgram/dl, reduced significantly the IRI portal level and the IRI secretion induced by glucose or arginine, whereas basal or stimulated IRG levels are not modified. The ratio IRI:IRG is diminished in each group perfused with NH4+ acetate. Our results show that ammonia inhibits insulin without modifications in the glucagon secretion; hyperglucagonemia and hyperinsulinism reported in hepatic encephalopathy with chronic hyperammonemia may not be attributed to an effect of ammonia.