FIG. 5.

Intraportal 30-min insulin delivery protocol in rats (rat protocol 4). A: Rats were anesthetized and indwelling catheters were placed into the mesenteric vein, jugular vein, and carotid artery. B: Rats received a constant infusion of somatostatin (10 μg/kg/min) for 30 min to inhibit endogenous insulin release. Insulin was infused directly into the portal vein at the rate of 70 pmol/kg/min either in a typical pulsatile pattern, in a same-rate constant insulin infusion, or as an insulin infusion selected to reproduce that observed in patients with evolving diabetes (∼50% decrease in pulse mass). A variable infusion of 50% dextrose was given intravenously to match systemic plasma glucose concentrations among the three groups. Sequential hepatic biopsies were obtained at 0 and 30 min after the start of insulin infusion protocols. Plasma glucose (C), free fatty acid (D), and mean glucose infusion rates (E) required to match plasma glucose levels among the three infusion protocols. Data are mean ± SE. *P < 0.05 vs. pulsatile.