Histamine receptor-mediated calcium ion movement in a receptor-rich microsomal fraction

The histamine receptor-rich microsomal fraction from the longitudinal muscle of cat small intestine, which consists of membrane vesicles, was loaded with 45Ca ions and the Ca ion efflux from it was examined. Histamine increased the efflux of 45Ca ions. The effect of histamine was blocked by diphenhydramine. Histamine had no effect on the histamine receptor-free microsomal fraction from dog small intestine muscle. This suggests that the ion movement may be mediated by histamine receptors.