Intestinal gradient of enterokinase activity in different species of animals.

The proximodistal gradient of enterokinase activity was studied in mucosal homogenates of the duodenum, jejunum, ileum, caecum (or megacaecum) and sigmoid flexure of various mammals. The study was carried out in groups of 5 monkeys, guinea pigs, dogs and rats and also in gnotobiological rats--conventional (n = 5), germ-free (n = 10) and monocontaminated (n = 5) with Escherichia coli 0 86. Enterokinase activity was likewise determined in duodenal mucosal homogenates prepared from material resected at operation from adult humans (n = 5) and from a group of monkeys (n = 5), with and without the addition of Triton X-100. Enzymatic activity was determined by a modification of Nordström and Dahlqvist's method, using pH-stat titration. In all the animals, enterokinase values were unequivocally the highest in the duodenal mucosa; in the other intestinal segments it displayed a marked aboral decrease, so that we found about 30% of duodenal activity in the jejunum, trace amounts in the ileum and zero values in the caecum and the sigmoid flexure. In the individual animals, the enterokinase activity values fell in the sequence monkey greater than guinea-pig greater than dog greater than rat. Enterokinase activity in the human duodenum was practically the same as in the rat duodenal mucosa. No reciprocal differences were found in gnotobiological rats. Either whole homogenate or the supernatant of triton-treated homogenate can be used for the demonstration of enterokinase in laboratory practice. The only part which can be employed for diagnostic purposes in duodenal mucosa.