Abstract
A considerably wide range of fasting plasma immunoreactive glucagon (IRG) values has been obtained in healthy subjects using a conventional radioimmunoassay technique even with antiserum 30K, specific for pancreatic glucagon. This wide variation appears, at least in part, to be caused by the presence of non-specific factors in plasma amples which interfere with the glucagon-glucagon antibody reaction and eventually give falsely high IRG values. A correction can be made for this adverse effect by subtracting correction factor (CF) from the “IRG values” of a given plasma sample read against a standard curve obtained by serial dilution of standard glucagon with veronal buffer containing bovine serum albumin. The CF is determined by reading apparent IRG values of glucagon free plasma (GFP) prepared for each sample against a standard curve.
This communication describes a simple and reliable method for the preparation of GFP. 1.5ml of a plasma sample and 60μl of veronal buffer are incubated with 150mg of cellulose powder MN 300HR for 1 hour at room temperature. The incubation is interrupted very 10min by complete mixing with vortex mixer. One ml of supernatant obtained with centrifugal separation at 2500r.p.m. for 20min is transfered to a tube containing 1000 K. I. U. of lyophilized Trasylol and stored at -20° until ssay.
Fasting 1RG levels in 14 healthy subjects determined with the present method using CF were 37±23 (mean±1S.D.) pg/ml, ranging 12 to 96 pg/ml, while the values without using CF were 223±154pg/ml, ranging 78 to 630pg/ml. Therefore, it seems to be quite reasonable to apply the present method to IRG determination.
