Role of a negative arterial-portal venous glucose gradient in the postexercise state

Prior exercise stimulates muscle and Liver glucose uptake. A negative arter ial-portal venous glucose gradient (a-pv grad) stimulates resting net hepat ic glucose uptake (NHGU) but reduces muscle glucose uptake. This study inve stigates the effects of a negative a-pv grad during glucose administration after exercise in dogs. Experimental protocol: exercise (-180 to -30 min), transition (-30 to -20 min), basal period (-20 to 0 min), and experimental period (0 to 100 min). In the experimental period, 130 mg/dl arterial hyper glycemia was induced via vena cava (Pe, n = 6) or portal vein (Po, n = 6) g lucose infusions. Insulin and glucagon were replaced at fourfold basal and basal rates. During the experimental period, the a-pv grad (mg/dl) was 3 +/ - 1 in Pe and -10 +/- 2 in Po. Arterial insulin and glucagon were similar i n the two groups. In Pe, net hepatic glucose balance (mg kg(-1) min(-1), ne gative = uptake) was 4.2 +/- 0.3 (basal period) and -1.2 +/- 0.3 (glucose i nfusion); in Po it was 4.1 +/- 0.5 and -3.2 +/- 0.4, respectively (P < 0.00 5 vs. Pe). Total glucose infusion (mg kg(-1) min(-1)) was 11 +/- 1 in Po an d 3 +/- 1 in Pe (P < 0.05). Net hindlimb and whole body nonhepatic glucose uptakes were similar. Conclusions: the portal signal independently stimulat es NHGU after exercise. Conversely, prior exercise eliminates the inhibitor y effect of the portal signal on glucose uptake by nonhepatic tissues. The portal signal therefore increases whole body glucose disposal after exercis e by an amount equal to the increase in NHGU.