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Relationship between arterial and portal vein immunoreactive glucagon during exercise
D H Wasserman1, D B Lacy, D P Bracy
1Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1993
Summary
Portal vein glucagon levels, not arterial, are key for regulating liver glucose production during exercise. Increased splanchnic glucagon release significantly contributes to exercise-induced hepatic glucose production.
Area of Science:
- Physiology
- Endocrinology
- Exercise Metabolism
Background:
- Arterial immunoreactive glucagon (IRG) changes may not accurately reflect hepatic glucose production regulation during exercise.
- Portal vein (PV) IRG is more relevant due to its direct supply to the liver, comprising ~80% of liver blood flow.
Purpose of the Study:
- To determine if arterial IRG reflects portal vein IRG levels in dogs during rest and exercise.
- To assess the contribution of splanchnic IRG release to hepatic glucose production during exercise.
Main Methods:
- Dogs (n=5) were instrumented with arterial, hepatic vein (HV), and PV catheters.
- Hepatic plasma flow (HPF) and hepatic glucose production (Ra) were measured using indocyanine green and [3-3H]glucose infusion.
- IRG levels were measured in arterial, HV, and PV blood during rest and 150 minutes of treadmill exercise.
Main Results:
- IRG levels were significantly higher in the PV compared to the artery and HV at rest and during exercise.
- Exercise increased IRG levels in all vessels, with the greatest rise observed in the PV.
- A decrease in HPF during exercise accounted for less than 11% of the increased arterial-to-PV IRG gradient; increased splanchnic IRG release explained the remainder.
- Hepatic glucose production (Ra) showed a linear relationship with IRG levels in all three measured vessels.
Conclusions:
- Portal vein IRG, not arterial IRG, is a more accurate indicator of glucagon's role in regulating hepatic glucose production during exercise.
- Increased splanchnic IRG release plays a significant role in augmenting hepatic glucose production during exercise.