The pancreas releases insulin in a pulsatile manner; however, studies assessing the livers response to insulin have used constant infusion rates. Our aims were to determine whether the secretion pattern of insulin (continuous vs. pulsatile) in the presence of hyperglycemia 1) influences net hepatic glucose uptake (NHGU) and 2) entrains NHGU. Chronically catheterized conscious dogs fasted 42 h received infusions including: peripheral somatostatin, portal insulin (0.25 mU/kg/min), peripheral glucagon (0.9 ng/kg/min), and peripheral glucose at a rate to double the glucose load to the liver. After the basal period, insulin was infused for 210 min at either 4 x the basal rate (1 mU/kg/min) or an identical amount in pulses of 1 and 4 min in duration followed by intervals of 11 and 8 min (CON, 1/11, 4/8, respectively) in which insulin was not infused. A variable peripheral glucose infusion containing ³H-glucose clamped glucose levels at twice the basal level (~200 mg/dl) throughout each study. Hepatic metabolism was assessed by combining tracer and arteriovenous difference techniques. Arterial plasma insulin [µU/ml] increased from basal levels of 6±1 either to a constant level of 22±4 in CON or oscillated from 5±1 to 416±79 and from 6±1 to 123±43 in 1/11 and 4/8, respectively. NHGU (-0.8±0.3, 0.4±0.2 and -0.9±0.4 mg/kg/min) and net hepatic fractional extraction of glucose (0.04±0.01, 0.04±0.01 and 0.05±0.01) were similar during the experimental period. Spectral analysis was performed to assess whether a correlation existed between the insulin secretion pattern and NHGU. NHGU was not augmented by pulsatile insulin delivery and there is no evidence of entrainment in hepatic glucose metabolism. Thus, the loss of insulin pulsatility per se likely has little or no impact on the effectiveness of insulin in regulating liver glucose uptake.