Nippostrongylus brasiliensisin the rat: Failure to relate intestinal histamine and mast cell levels with worm expulsion

Abstract

This paper describes experiments to determine whether intestinal tissue mast cells and/or intestinal histamine are involved in the second, expulsive step of worm elimination. In neonatal rats, intestinal tissue contains only very little histamine and mature mast cells are encountered only sporadically. From birth to the adult age, there was a gradual rise in both intestinal mast cells and histamine.DuringNippostrongylus brasiliensisinfection in the adult rat, the concentration of histamine in the small intestine was clearly lower than in uninfected controls.Especially low histamine values were found to occur on days 6–12 of a primary infection in the region where the main worm burden was located. Similarly, the number of tissue mast cells present in the epithelium of the jejunum was decreased in the same region and during the same period of time. From the observation that the bulk of the parasites are expelled at a time when histamme and mast cell levels are low, it was concluded that mast cells and their constituents were not an essential factor in the second step of worm eliminationThis work was supported by the Schweizerische Nationalfonds zur Förderung der wissenschaftlichen Forschung (Grant 5200.3). The skilful technical assistance of Miss I. Beeger, Miss R. Keist and Miss M. Iseli is gratefully acknowledged. I thank Mr H. Berchtold, Biostatistisches Zentrum der Universität Zürich, for the statistical evaluation of the data.