Distribution of histamine in the lumen contents of the small intestine of uninfected and Hymenolepis diminuta-infected rats.

Using a specific radioenzymatic assay, histamine was detected and measured in the lumen contents of six different segments of the small intestine of uninfected rats and rats infected with Hymenolepis diminuta as well as in worm tissues. The distribution of histamine in the lumen of the small intestine of uninfected rats was found to range from 1.4 +/- 0.1 microM in the first (anterior) segment to 0.59 +/- 0.13 mM in the sixth (posterior) segment. There were no significant differences between these concentrations and those found in the lumen contents of intestine from rats infected with H. diminuta. On the other hand, although most H. diminuta was confined to the second and third segments, the concentration of histamine associated with the worm tissues (5.4 +/- 0.4 microM) was significantly lower than that in Hymenolepis-containing intestinal segments. The data suggest that established infections of H. diminuta do not cause a significant increase in histamine levels in host's intestinal lumen, nor do they affect the spatial gradient in the lumen.