TY - JOUR T1 - EXPERIMENTAL STUDIES ON HEART TONICS III. THE RELATIONSHIPS OF CALCIUM IONS, HYDROGEN IONS AND DIGITALIS JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 111 LP - 128 VL - 39 IS - 1 AU - WILLIAM NYIRI AU - LOUIS DUBOIS Y1 - 1930/05/01 UR - http://jpet.aspetjournals.org/content/39/1/111.abstract N2 - The paper deals with the question as to what pharmacological relation digitalis, Ca++ and H+ bear to each other. 1. Full digitalis and ouabain action takes place in the absence of Ca++. 2. Increase of the calcium level to three or four times the physiological concentration reinforces the effect of digitalis on the heart muscle and brings about quicker action. 3. Digitalis also enhances the effect of an increased calcium concentration of the blood and nutrient fluid. 4. Experiments with the ash of digitan show that its calcium content is very small and does not materially influence the action of the drug. 5. Changes of the H+ concentration of the nutrient fluid within the range of 5.2 to 7.6 do not influence the action of the heart. The heart muscle has an efficient protective self control in order to maintain the physiological H+ of the surrounding fluid. Only an H+ beyond this range impairs or abolishes the heart beats. 6. The action of digitalis is not influenced by changes of the pH of the perfusing fluid within the range of 5.2 to 7.6. 7. Typical digitalis poisoning also takes place when the heart works under the combined influence of calcium and atropine as well as of calcium and adrenaline. 8. The range of variation in the response of the frog heart to the action of digitalis is not decreased under the simultaneous influence of calcium with atropine or with adrenaline. The results of the above investigations lead us to the conclusion that calcium and digitalis are not essentially related in their pharmacological action. The similar features of their effect on the heart, however, justify, from the experimental viewpoint, their combined use in therapeutics. Strophanthin and the digitalis glucosides have an action sui generis on the heart. ER -