Role of hepatic nerves in response of liver to intraportal glucose delivery in dogs

Abstract

Net hepatic glucose uptake (NHGU) is much greater during oral or intraportal glucose loading than during peripheral intravenous glucose delivery even when similar glucose loads and hormone levels reaching the liver are maintained. To determine whether this difference is influenced by the hepatic nerves, nine conscious 42-h-fasted dogs in which a surgical denervation of the liver (liver norepinephrine levels postdenervation averaged 2.4% of normal) had been performed were subjected to a 40-min control period and two randomized 90-min test periods during which somatostatin (0.8 microgram.kg-1.min-1), intraportal insulin (1.2 mU.kg-1.min-1), and intraportal glucagon (0.5 ng.kg-1.min-1) were infused. The glucose load to the liver was increased twofold by infusing glucose into a peripheral vein (Pe) or the portal vein (Po). Arterial insulin and glucagon concentrations were 39 +/- 2 and 39 +/- 3 microU/ml and 55 +/- 5 and 54 +/- 7 pg/ml during Pe and Po, respectively. The hepatic glucose loads were 50.3 +/- 4.4 and 51.4 +/- 5.8 mg.kg-1.min-1 while NHGU was 2.1 +/- 0.5 and 2.2 +/- 0.7 mg.kg-1.min-1 during Pe and Po, respectively. Similar hormone levels and glucose loads reaching the liver in dogs with intact hepatic nerve supplies were previously shown to be associated with NHGU of 1.4 +/- 0.7 and 3.5 +/- 0.8 mg.kg-1.min-1 in the presence of peripheral and portal glucose delivery, respectively. In conclusion, an intact nerve supply to the liver appears to be vital for the normal response of the liver to intraportal glucose delivery.