In the present study we characterized and compared the different molecular forms of
glucagon-like immunoreactivity in extracts of peripheral plasma and hepatic
metastases of a patient with pancreatic alpha-cell
tumor. Plasma and
tissue extracts were chromatographed on
Sephadex G-50 columns. Immunoreactivity in the eluting fractions was assayed with an anti-
glucagon antiserum that specifically recognizes the C-terminal region of the pancreas
glucagon molecule. Total plasma
glucagon-like immunoreactivity prior to surgery was 26.64 nmol/l and consisted of four peaks of immunoreactivity of apparent 9,000 mol wt, 5,800-5,400 mol wt, and 4,000 mol wt. Total
glucagon-like immunoreactivity extracted from the hepatic
metastasis was 47.41 nmol/g wet weight and eluted as two major peaks of immunoreactivity as follows: peak I, mol wt 3,800, corresponding to "true" 3,500 mol wt
glucagon; peak II, mol wt 1,400, probably consisted of
glucagon degradation products. The results clearly demonstrated that both plasma and
glucagon-like immunoreactivity extracted from hepatic
metastases were heterogeneous and comprised species corresponding not only to "true"
glucagon but also to higher mol wt forms. The lack of higher mol wt forms of immunoreactivity in the hepatic
metastases of the
alpha-cell tumor suggests that this metastatic
tumor tissue may contain an
enzyme capable of converting the higher mol wt forms to smaller
glucagon-like components whereas this degradative system seems to be defective in the primary
tumor.