Effect of Calcium on Cardiac Reactions to Mercury.

Abstract

The response of the isolated frog heart to mercury in normal Ringer was first studied by Salant and Kleitman, 1 but as far as we are aware no investigation has been previously reported on the effect of mercury in solutions containing different amounts of calcium. Experiments were therefore carried out with this object in view, Straub's method being used.

After trying different concentrations of mercury, we found that a solution of 1:100,000 in normal Ringer, containing 0.012% calcium chloride, best served the purpose as a basis of comparison. The immediate effect of this amount of mercury was not constant, no changes being observed in most cases, and moderate depression only occurred in some experiments, thus corroborating the observations of Salant and Kleitman, which were made with Simpson's method, modified by his pupil, Livingston. We noticed, however, that in some experiments a gradual decline, especially in the strength of the contractions, occurred, and at the end of one to 3 hours, the amplitude showed a considerable decrease. When the amount of calcium chloride in Ringer's solution was reduced from the normal 0.012 to 0.008 and 0.006% the resistance to mercury was greatly decreased. In a concentration of 1:100,000 (as the chloride) it produced a well marked decrease of the strength of the contractions, the effect setting in after a short latent period, and within 3 or 4 minutes the amplitude was reduced in some experiments 50% or more. The rate was also decreased but to a much smaller extent. Drastic reduction in the strength of the contractions was observed in some of these experiments. The effect occurred almost immediately after the introduction of mercury, the depression increasing rapidly and after one minute the contractions became very feeble.