Relative abundance of big and little gastrins in the tumours and blood of patients with the Zollinger Ellison syndrome.

The relative concentrations of big gastrin (G-34) and little gastrin (G-17) were compared in the sera and tumours (gastrinomas) of Zollinger-Ellison syndrome patients. Big and little gastrins were identified in all 10 serum samples and in all 10 tumour biopsies examined. In serum, G-34 (range of concentrations 58-220 000 fmol/ml) was the major form of gastrin and G-17 (22-78 000 fmol/ml) was a minor component; the mean relative abundance of G-17/[G17 + G34]) in serum was 0-18 and the mean relative abundance of G-34 was 0-82. In tumour, however, the opposite was true: G-17 (49-869 000 pmol/g) was the major component and G-34 (45-464 pmol/g) a minor component, and the relative proportions of G-17 and G-34 were 0-73 and 0-27 respectively. Following an intravenous injection of porcine secretin (2-0 U/kg) there was a rapid increase in concentration of all forms of gastrin in the blood, but the increase in G-17 was proportionately greater than that of G-34 (relative abundance of G-17 in basal serum was 0-21 compared with 0-37, five minutes after secretin). Differences in the half lives of G-17 and G-34 may partly explain their relative abundancies in serum and tumour tissue.