EVALUATION AND CLINICAL-APPLICATION OF THE ENTEROTEST(R) FOR THE DETERMINATION OF HUMAN BILIARY PORPHYRIN COMPOSITION

The Enterotest(R) string test is an easy and non-invasive method for s ampling duodenal fluid, which has been successfully used for the analy sis of duodenal microflora, as well as biliary bile acid and lipid com position. The method was evaluated for determination of porphyrins in duodenal bile in normal subjects and subjects with porphyria, followin g cholecystokinin induced gall bladder contraction; it is known that a nalysis of biliary porphyrins is more discriminatory for the diagnosis of asymptomatic porphyria than their analysis in faeces or urine. Mor eover, serial analysis of bile from patients with erythropoietic proto porphyria may help in establishing their ability to secrete protoporph yrin in bile and to assess effects of treatment. The binding of variou s porphyrins to Enterotest(R) strings was investigated by incubating p ieces of the string in different human bile samples with low to very h igh porphyrin concentrations, followed by HPLC analysis of porphyrins both in the native bile and in extracts obtained from the strings. No differences between porphyrin composition in native bile and extracts were observed. Duodenal fluid obtained by means of the Enterotest(R) f rom volunteers not receiving cholecystokinin showed large variations i n porphyrin patterns not resembling those of native bile. Mesoporphyri n, a secondary porphyrin derived from protoporphyrin by bacteria, was often detectable. These data indicate that the duodenal content withou t cholecystokinin injection does not reflect biliary porphyrin composi tion. The presence of mesoporphyrin in the whole intestinal tract, but not in serum and bile, suggests that there is no enterohepatic circul ation of secondary porphyrins. There was close agreement between the p orphyrin ratios found with the standard duodenal intubation technique and the Enterotest(R), performed simultaneously in one healthy volunte er after induction of gall bladder contraction by cholecystokinin. Fro m these experiments, it was concluded that fluid adsorbed to the Enter otest(R) string after gall-bladder contraction can be used to determin e biliary porphyrin composition. Since duodenal bile is diluted gall b ladder bile, variable porphyrin concentrations were found when applyin g the Enterotest(R) in combination with cholecystokinin in the same su bject on successive days. However, porphyrin ratios, such as the proto porphyrin to coproporphyrin I ratio, were relatively constant. In subj ects with symptomatic variegate porphyria, the Enterotest(R) showed hi ghly aberrant porphyrin patterns, with increased protoporphyrin to cop roporphyrin I ratios and, in addition, the presence of some unknown po rphyrins. A deviating biliary protoporphyrin/coproporphyrin I ratio in one patient appeared to be a useful diagnostic index for the presence of latent variegate porphyria (or variegate porphyria in remission). Finally, the Enterotest(R) method is also useful for monitoring patien ts with erythropoietic protoporphyria for their ability to secrete pro toporphyrin via bile, evaluated by measurement of protoporphyrin/copro porphyrin I and III ratios in Enterotest(R) strings. We conclude that the Enterotest(R) is a valuable tool for investigating porphyrin metab olism and biliary secretion in humans.