Characteristics of cardiac tissue from adrenalectomized rats

¹ Department of Physiology, University of Illinois College of Medicine, Chicago, Illinois

In vitro measurements of strength-duration curves, refractory periods, isometric developed and passive length-tension diagrams, and active and resting respiratory rates were made on left ventricular muscle columns from 18 normal and 17 bilaterally adrenalectomized rats. The adrenalectomized rats were given saline for 5–7 days following adrenalectomy, and sacrificed after an additional 6–8 days without saline. Electrocardiograms, growth curves, heart-body weight ratios and nitrogen content of heart tissue were recorded for all control and experimental animals. Strength-duration curves, refractory periods, and developed and passive length-tension diagrams of heart columns from adrenalectomized animals did not differ statistically from normal, but resting respiratory rates were significantly increased. Results indicate that adrenal insufficiency lowers the in vitro efficiency of cardiac function by greatly increasing the metabolism of the myocardium without altering its contractility.