A NEGATIVE ARTERIAL-PORTAL VENOUS GLUCOSE GRADIENT DECREASES SKELETAL-MUSCLE GLUCOSE-UPTAKE

The effect of a negative arterial-portal venous (a-pv) glucose gradien t on skeletal muscle and whole body nonhepatic glucose uptake was stud ied in 12 42-h-fasted conscious dogs. Each study consisted of a 110-mi n equilibration period, a 30-min baseline period, and two 120-min hype rglycemic (2-fold basal) periods (either peripheral or intraportal glu cose infusion). Somatostatin was infused along with insulin (3 x basal ) and glucagon (basal). Catheters were inserted 17 days before studies in the external iliac artery and hepatic, portal and common iliac vei ns. Blood flow was measured in liver and hindlimb using Doppler flow p robes. The arterial blood glucose, arterial plasma insulin, arterial p lasma glucagon, and hindlimb glucose loads were similar during periphe ral and intraportal glucose infusions. The a-pv glucose gradient (in m g/dl) was 5 +/- 1 during peripheral and -18 +/- 3 during intraportal g lucose infusion. The net hindlimb glucose uptakes (in mg/min) were 5.0 +/- 1.2, 20.4 +/- 4.5, and 14.8 +/- 3.2 during baseline, peripheral, and intraportal glucose infusion periods, respectively (P < 0.01, peri pheral vs. intraportal); the hindlimb glucose fractional extractions ( in %) were 2.8 +/- 0.4, 4.7 +/- 0.8, and 3.9 +/- 0.5 during baseline, peripheral, and intraportal glucose infusions, respectively (P < 0.05, peripheral vs, intraportal). The net whole body nonhepatic glucose up takes (in mg.kg(-1).min(-1)) were 1.6 +/- 0.1, 7.9 +/-: 1.3, and 5.4 /- 1.1 during baseline, peripheral, and intraportal glucose infusion, respectively (P < 0.05, peripheral vs. intraportal). In the liver, net glucose uptake was 70% greater during intraportal than during periphe ral glucose infusion (5.8 +/- 0.7 vs. 3.4 +/- 0.4 mg.kg(-1).min(-1)). In conclusion, despite comparable glucose loads and insulin levels, hi ndlimb and whole body net nonhepatic glucose uptake decreased signific antly during portal venous glucose infusion, suggesting that a negativ e a-pv glucose gradient leads to an inhibitory signal in nonhepatic ti ssues, among which skeletal muscle appears to be the most important.