Radioimmunoassay for vasoactive intestinal polypeptide (VIP) in plasma before and during endoscopic examinations

A specific and sensitive radioimmunoassay of human vasoactive intestinal polypeptide using synthetic VIP as standard preparation and antiserum to synthetic VIP R 502 (Yanaihara et al. 15) is described. No crossreactions with a number of other gastrointestinal hormones such as glucagon, secretin, GIP, HPP or substance P was detected. Aprotinin (Trasylol, Bayer) or heparin had no influence on the antigen--antibody reaction. High concentrations of sodium or potassium chloride in plasma, or hyperlipoproteinemia, did not interfere with the antiserum in the described system. Basal plasma concentration of VIP in 18 females (means +/- sem = 24.05 +/- 1.79 VIP/l) and 20 males (means +/- sem = 24.11 +/- 1.91 pmol/l VIP) showed no sex specific variations. During gastroscopy plasma VIP levels were significantly higher than basal values, showing a peak secretion when the gastric antrum was inspected. During the entire colonoscopic examination, VIP levels were significantly higher than basal values. Endoscopic examination may possibly liberate VIP from the VIP containing cells which can be found throughout the gastrointestinal tract.