Electrical and Mechanical Changes in Isolated Heart Following Changes in Calcium Content of Perfusing Fluid

Abstract

The experiments here reported were performed on the isolated heart of the rabbit perfused at 38°C. by the method described by Locke, but without recirculation of fluids. Changes in amplitude of contraction were recorded on a drum, and electrical changes were recorded with a string galvanometer from one circuit only, the connections being made through non-polarizable electrodes to the aorta and to the apex.Because of the known unphysiological nature of Locke's solution the solutions used for perfusion were based upon those described by van Dyke and Hastings, with the addition, in many instances, of sodium citrate and a higher total calcium concentration. In these solutions the calcium ion concentration has been calculated from the dissociation constant of calcium citrate as simultaneously reported. The solution used as the standard of reference usually contained 0.7 millimol of calcium ions per liter, and 0.8 millimol per liter of non-ionized calcium in the form of calcium citrate.In solutions without citr...