Circulating Glucagon Plasma Profiles and Metabolism in Health and Disease

Abstract

Plasma immunoreactive glucagon (IRG) comprises a number of fractions with different MW. The patterns of IRG components are reviewed in normal subjects and in patients with renal failure, diabetes mellitus, glucagonoma and other conditions. The role of the kidneys and the liver in the metabolism of glucagon is discussed. Circulating immunoreactive glucagon is heterogeneous, consisting of at least 4 fractions: A: > 40,000 daltons; B: 9000 daltons; C: 3500 daltons; and D: < 2000 daltons. Metabolism of glucagon occurs primarily in the liver and kidney. The liver extracts the 3500-dalton fraction but not the other components. The kidney metabolizes both the 3500-dalton fraction (by glomerular filtration and peritubular uptake) and the 9000-dalton component (by peritubular uptake). The metabolic handling of pancreatic .beta.-cell and .alpha.-cell peptides appears to be similar.