Radioimmunoassay of Human Pepsinogen A and Pepsinogen C

Publisher Website
Google Scholar
Abstract
We describe the development of radioimmunoassays to measure both human pepsinogen A and pepsinogen C concentrations in serum. The antibodies were raised in goats by immunization with purified pepsinogen A or C. The affinity constants of the respective antibodies were 20 .cntdot. 1010 l/mol and 7 .cntdot. 1010 l/mol. Pepsinogens A and C were labeled with Na 125I by the chloramine T method. The binding between labels and antibodies was inhibited by 0.50 at 0.82 ng pepsinogen A per tube and 2.1 ng pepsinogen C per tube. The detection limits of the assay of pepsinogen A and C were 0.12 .mu.g/l and 1.8 .mu.g/l, respectively. Pepsinogen A and C were purified and added to a patient serum, showing a good recovery in the radioimmunoassays. Serial dilution of another patient serum, which contained a high concentration of both antigens, showed curves parallel to the standard curves. The intra- and interassay variations of these radioimmunoassays were evaluated. The intra-assay coefficients of variation for pepsinogen A were found to vary from 0.03 to 0.102 at concentrations in serum in the normal range, while the inter-assay coefficient of variation ranged from 0.118 to 0.194 at the same concentrations in serum. For the pepsinogen C radioimmunoassay we found intra-assay coefficients of variation between 0.126 and 0.147 at concentrations in serum in the normal range, while the inter-assay coefficient of variation ranged from 0.174 to 0.325 for the same sera. In 201 blood donors we found a mean serum concentration of pepsinogen A of 59 .mu.g/l and a mean serum concentration of pepsinogen C of 15 .mu.g/l. There was a significant relationship between these values (r = 0.779, p < 0.001). The concentrations of both pepsinogens were increased in 10 patients with duodenal ulcer (132 and 67 .mu.g/l, respectively). Serum pepsinogen A was decreased in 14 patients with partial gastrectomy (34 .mu.g/l) and in 6 with achlorhydria (9 .mu.g/l), accompanied by raised (34 .mu.g/l) and normal (20 .mu.g/l) mean pepsinogen C concentrations in the respective groups. In 4 patients with a total gastrectomy the mean serum concentration of both pepsinogen A and C reached the zero level (5 and 4 .mu.g/l, respectively). These results not only underline the accuracy of the measurements but also point to their clinical relevance.