Effect of Various Ions upon the Heart Rhythm of Crayfish (Cambarus clarkii).

Abstract

Using perfusing solutions of various salts approximating in ionic concentrations those found by Griffith 1 to be present in the blood of Astacus fluviatilis, an attempt was made to determine the effect of the Na, K, Ca, and Mg ion upon the intact heart of the Crayfish (Cambarus clarkii). For comparative purposes a control perfusing solution containing 1% NaCl+0.028%—KCl+0.024% CaCl₂ was employed. Such a solution applied to the heart maintained the normal rhythm for a period of several hours when perfused at a temperature of 25±0.1 degrees centigrade. Graphic records were obtained of the heart rhythm while being perfused with the various solutions.

In determining the effect of the Na ion, 3 perfusing solutions were employed, viz.: A pure solution of 1% NaCl, one containing 2% NaCl+0.028% KCl+0.024% CaCl₂ and one containing 0.028% KCl+0.024% CaCl₂. Both solutions containing Na produced a marked increase in rate and amplitude of the beats coupled with a loss in tone. The pure 1% solution had an especially marked effect upon the tone. The solution lacking Na produced a sharp increase in the tone accompanied by a loss in amplitude and rate, the heart generally stopping in diastolic arrest in less than 20 minutes. It may be noted in this connection that Carlson, 2 working upon Limulus, found that the Na stimulates the heart and increases the amplitude of the beats. Hogben 3 noted that in Maia and Homarus a pure solution of NaCl produced an almost immediate increase in tone, resulting shortly in systolic arrest. Rogers 4 observed that NaCl had the power of restoring rhythmatic contractions in the heart of the crab (Brachnotus nudus). It is concluded from the present work that the Na ion increases the rate and amplitude and decreases the tone of the crayfish heart and is, therefore, concerned in the regulation of normal heart rhythm.

Similar experiments were performed with solutions of KCl and CaCl₂. A pure solution of 0.024% CaCl₂ produced a sharp increase in tone and a slight decrease in the rate. Increasing the CaCl₂ the control perfusing solution affected the rate only, the latter being decreased slightly. A pure solution of 0.028% KCl invariably depressed the rate and amplitude but had slight if any effect upon the tone. The removal of K from the control perfusing solution resulted in systolic arrest of the heart in less than 30 minutes. Normal rhythm could subsequently be restored only upon the replacement of KCl in the perfusing solution. In regard to the effect of K and Ca upon the heart rhythm of other closely related species, Hogben 3 finds that in Maia an excess of K produces systolic arrest of the heart. Carlson 2 observed that K and Ca both produced depressor action upon Limulus heart muscle. The present work is similar to the above in that K and Ca depress the rate and amplitude and increase the tone of the Crayfish heart, the Ca ion having an especially pronounced effect upon the tone.