Interference by Gastrografin with a spectrophotometric trypsin assay.

Small quantities of Gastrografin remaining in the intestinal tract some hours after introduction have been shown to cause falsely low trypsin values as determined by a spectrophotometric assay system. This interference is due first to the high absorbance of Gastrografin at 254 nm resulting in a falsely high background optical density. Secondly, Gastrografin inhibits esterase activity towards the synthetic substrate used in this assay. Gastrografin did not interfere with gelatin proteolysis by trypsin and did not affect amylase or lipase determination. Thus the instillation of Gastrografin into the duodenum before pancreatic function tests should be avoided when the trypsin content is to be determined spectrophotometrically.