A liver factor increasing glucose uptake in rat hindquarters

The effect of the liver on glucose uptake in muscle was studied in the isolated rat hindquarter, perfused with and without an isolated rat liver included in a recirculating system. Glucose uptake in the hindquarter was 0.75 +/- 0.10 mumol.min-1 x 100 g bw-1 (mean and SEM), and increased to 1.30 +/- 0.12 during the period when the liver was included in the perfusion (N = 17; p = 0.0001). In experiments where tissue extracts were added to the perfusate during the second period, raw liver extracts increased the glucose uptake from 0.87 +/- 0.11 to 1.25 +/- 0.10 (N = 6; p = 0.003). Deproteinized liver and kidney extracts increased glucose uptake similarly. When the liver and hindquarter were perfused together during the first period, the glucose uptake in the hindquarter was 1.55 +/- 0.16 mumol.min-1 x 100 g bw-1 and decreased gradually during the period of isolated perfusion to 1.27 +/- 0.16 (N = 4; p = 0.15). In control experiments where tissue free extract fluid was added to the perfusate during the second period, or where the hindquarter was perfused either alone or with the liver during both periods, glucose uptake decreased slightly from 0.87 +/- 0.18 to 0.80 +/- 0.13 (N = 9; p = 0.2). In conclusion, a factor from the liver may increase the glucose uptake in muscle tissues. This factor is present in extracts from the liver and kidney, it is probably not a protein, but its nature is not known. It is speculated that glucose intolerance in patients with liver disease may be related to a lack of this factor.