Nature of plasma immunoreactive glucagon in man.

Since an immunoassay technique was first applied for measurement of glucagon, many studies on circulating glucagon levels under various conditions have been conducted. Their results, however, are not necessarily unanimous, as suggested by the fact that more than twenty fold differences in plasma immunoreactive glucagon (IRG) values in fasting healthy subjects have been reported. (Schalch, 1966; Aguilar-Parada et al., 1969) Several factors are considered to be responsible for the wide range of reported plasma IRG concentrations in the basal condition. One possible factor may be connected with the problem of the concomitant presence in plasma of an IRG of extrapancreatic as well as pancreatic origin, as suggested in the studies of Samols et al.(1966) and Valverde et al. (1967, 1970 a and b). Plasma IRG levels of normal subjects reported by Aguilar-Parada et al.(1969), using an antiglucagon serum which reacted poorly with gut glucagon, were notably lower than those determined with antisera which might crossreact to a moderate degree with gut glucagon. These facts show that an unequal affinity of antiglucagon sera employed by various investigators for endogenous gut and pancreatic glucagon might be one of the causes for the striking differences in normal plasma IRG levels. The present study was undertaken to throw light on this problem by using two different antiglucagon sera which reacted with gut glucagon to varying degrees.