Plasma concentrations of glucose (A), insulin (B), and C-peptide (C) in five healthy subjects studied in the fasting state and during an intravenous glucose infusion (2 mg · kg−1 · min−1). Plasma glucose levels were obtained from blood samples from an arterialized vein. Insulin and C-peptide concentrations
were derived from blood samples obtained from an arterialized peripheral vein (dotted lines) and from the hepatic vein (continued
lines). Values are presented as means ± SEM (n = 5). P values were calculated by repeated-measures ANOVA.