The effect of calcium and magnesium ions on drug-receptor interactions

The effects of Ca and Mg on drug-receptor interactions were examined, using the taenia of the guinea pig and the rat vas deferens. The agonists, butyltrimethylammonium, histamine and noradrenaline protected their receptors from the block by the β-chloroethylamines in normal Locke-Ringer solution Ca-free Locke-Ringer solution and Mg-free Locke-Ringer solution but not in Locke-Ringer solution free of both Ca and Mg. On the other hand, the competitive antagonists, benactyzine methobromide and diphenhydramine protected their receptors from the block by the β-chloroethylamines in all the variations of Locke-Ringer solution used in this paper. These results indicate that Ca and Mg ions are involved in the combination of agonists with their receptors, but they are not involved in the combination of the competitive antagonists and β-chloroethylamines with their receptors. Mg ions may substitute for Ca ions in the agonist-receptor interactions.