Secretory Response and Immunochemical Heterogeneity of Glucagon in Plasma and Tumor Extracts of a Patient with Glucagonoma

Abstract

The secretory response and immunoreactive heterogeneity of glucagon was investigated in a patient with glucagonoma syndrome. After glucose administration, abnormal insulin release accompanied by glucose intolerance were observed, whereas the high glucagon circulating levels were only partially blocked after glucose or somatostatin infusion. Chromatographic fractionation of plasma samples, before and after arginine administration showed that most of the immunoreactivity eluted as true glucagon. Furthermore, when aliquots of the tumor extracts were fractionated by column chromatography or by polyacrylamide gel electrophoresis, most of the immunoreactivity eluted in the 3,500 molecular weight peak. In contrast with previous reports, our results indicate that neoplasia A cells can also manufacture and release into the bloodstream great amounts of genuine glucagon rather than larger glucagon immunoreactive forms. In spite of such findings, in this patient neither diabetes nor hyperglycemia were present.

Glucagonoma syndrome: a review and update on treatment

“…Fraction I (>60 000 daltons) is ‘big’ glucagon; fraction IV (3000 daltons) is ‘small’ glucagon. Fractions II (9000 daltons, ‘pro’ glucagon) and III (3500 daltons, ‘true’ glucagon) tend to be elevated in glucagonoma . The ‘pro’ glucagon likely represents the glucagon precursor from which both pancreatic and intestinal glucagon is derived.…”

“…The ‘pro’ glucagon likely represents the glucagon precursor from which both pancreatic and intestinal glucagon is derived. Both ‘pro’ and ‘true’ glucagon levels react similarly to the use of several treatment modalities . ‘Big’ glucagon has been found to be elevated in familial hyperglucagonemia …”