Influence of hydrocortisone on the action of sodium on isolated rabbit auricles

Abstract

Szent-Gyorgyi has demonstrated the importance of the 'intracellular ionic atmosphere' on the contraction of the cardiac muscle, and has suggested that adreno-cortical steroids may influence cellular activity by alterations in membrane permeability. It has also been shown by Selye and Renaud that the action of electrolytes on the heart is influenced by what is termed the 'conditioning' effect of hormones. Further, Holland has presented evidence to show that antiarrhythmic drugs act on the atria by depressing the transmembrane flux of sodium and potassium ions. In this connexion, it would be of interest to examine the effect of the steroid hormones on the action of the ions on the heart. It is well known that when the heart is kept in a medium containing sodium as the only ion it stops beating after some time. Later, when the medium is changed to Ringer solution, the beat recommences, presumably due to sodium extrusion. If a steroid hormone altered the permeability of the cell membrane, it would modify the action of sodium by interfering with sodium traffic across the membrane.