To study the consequences of hyperglycemia on glucose and nitrogen metabolism in cirrhosis, an hyperglycemic clamp was performed in 5 cirrhotic patients and 5 normal controls during two subsequent periods of 90 min, at 7.78 and then at 13.89 mmol/l. In the first period, glucose infusion and metabolic clearance rates were decreased in cirrhotics vs controls (p less than 0.05). In the second period, this difference between the two groups disappeared because of a more important enhancement in cirrhotics. Baseline plasma C peptide levels and those during hyperglycemia were the same during hyperglycemia in both groups, but plasma insulin level rose more in cirrhotics (p less than 0.05). Baseline insulin secretion following IV glucagon was reduced in cirrhotics vs controls (p less than 0.05), but became normal in the hyperglycemic state. Plasma glucagon levels were enhanced at all times in cirrhotics vs controls (p less than 0.01), but dropped more in cirrhotics vs controls (p less than 0.05). Insulin responsiveness, defined as the "glucose consumption: plasma insulin concentration" ratio was reduced in cirrhotics at 7.78 mmol/l (p less than 0.01), but was the same in both groups at 13.80 mmol/l because of a more important enhancement in cirrhotics, reflecting an improvement of insulin action probably at the post-receptor level and of non-insulin-mediated glucose transport. Hyperglycemia induced a drop in plasma concentration and muscular release of all aminoacids, excepted alanine, between the basal state and the end of the study. Aminoacid concentration rose only in cirrhotics, without any change in muscular output. In the same time, blood ammonia level rose only in cirrhotics, without reduction of muscular uptake.(ABSTRACT TRUNCATED AT 250 WORDS)