A portal‐arterial glucose concentration gradient as a signal for an insulin‐dependent net glucose uptake in perfused rat liver

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Abstract
Since in the usual perfusion of isolated rat liver via the portal vein an insulin‐dependent increase of hepatic glucose uptake could not be demonstrated, the possibility was considered that hepatic glucose uptake might not be a function of the absolute concentration of this substrate but of its concentration gradient between the portal vein and the hepatic artery. Therefore a new method was established for the simultaneous perfusion of isolated rat liver via both the hepatic artery (20–35% flow) and the portal vein (80–6596 flow). When glucose was offered in a concentration gradient, 9.5 mM in the portal vein and 6 mM in the hepatic artery, insulin given via both vessels caused a shift from net glucose release to uptake. This insulin‐dependent shift was not observed when glucose was offered without a gradient or with an inverse gradient, 6 mM in the portal vein and 9.5 mM in the hepatic artery. Using a portal‐arterial glucose gradient as a signal the liver might be able to differentiate between endogenous and exogenous glucose.