RELATION BETWEEN THE ACTION OF HISTAMIN, ATROPIN, ADRENALIN, AND HEAVY METALS ON THE INTESTINE

¹ From the Department of Physiology and Pharmocology, Duke University Medical School, Durham, North Carolina

1. There is a quantitative antagonism between histamin and atropin on the intestine of the guinea pig. If the amount of relaxation in millimeters caused by atropin is multiplied by the ratio of the amount of histamin to atropin a constant is obtained which in the case of the guinea pig has a value of 5.1. The curve obtained approximates a rectangular hyperbola.

2. The relaxation due to adrenalin is not a function of the amount of histamin, but only of the amount of adrenalin added. Therefore histamin and adrenalin are not acting on the same receptors in the muscle.

3. The effect of pH on the height of contraction due to histamin has been studied and it has been shown that the effect of changes of pH are reversible.

4. KCN causes immediate relaxation of muscle contracted by histamin, and because it reacts so quickly and in such small concentrations as M/20,000 the argument is against any respiratory mechanism being involved.

5. The height of contraction due to histamin is not affected by the absence of calcium, but the ability to maintain contraction is dependent on the presence of calcium on the surface of the muscle.

6. Heavy metals such as copper and lead cause contraction of the intestine only if calcium is present plus some substance like histamin. Without either of these substances, these metals are unable to produce contraction under the conditions of these experiments.