Metabolic fate of a gastric glucose load in unrestrained rats bearing a portal vein catheter.

Metabolic and hormonal responses to the administration of a gastric load of glucose (2.4 mg/g body wt) were evaluated after a fast of 6-7 h in unrestrained rats bearing a portal vein catheter. For the purpose of this study, we have designed a new technique for a direct catheterization of the portal vein that allows serial blood sampling in unrestrained Wistar rats. On the 6th postoperative day, food intake, body weight gain, liver function, histology of the liver, pancreas, intestine, and splanchnic blood flows were similar to those of sham-operated control rats. In the basal state glucose turnover was 21.3 +/- 0.9 mg.kg-1.min-1. After glucose ingestion, a portoperipheral gradient of lactate was present, reflecting the production of lactate by the intestine. Insulin secretion was biphasic and peaked at 12 min (344 +/- 46 microU/ml), whereas portal glucagonemia (400-500 pg/ml) remained unchanged. Sixty minutes after gastric glucose administration, 50% of the load was delivered at the periphery, and glucose utilization was increased by 100%. Hepatic glucose production decreased after 20 min and was inhibited by 30% at 60 min. Liver glycogen concentration remained unchanged during the experiment despite a normal capacity for glycogen synthesis.