Total plasma immunoreactive pancreatic glucagon (IRG) was measured in samples taken simultaneously from the proximal portal vein and superior vena cava of 26 healthy rats. The portal-peripheral ratio of IRG was 2.80±0.25, the portal-peripheral difference (Δ) 124±15 pg/ml, and percentage extraction 58±3. Gel filtration of paired portal and peripheral vein samples showed that reduction in the 3,500-dalton IRG component (glucagon) in peripheral samples accounted for almost all the differences, there being minimal and inconsistent changes in the high molecular weight (>40,000) fraction. The portal-peripheral ratio of the 3,500-dalton glucagon was 5.24±1.10, the portal-peripheral difference 130±33 pg/ml, and the percentage extraction 81±5.
Jonathan B. Jaspan, Alice H-J. Huen, Colin G. Morley, A. Rahim Moossa, Arthur H. Rubenstein