MECHANICAL PERFORMANCE AND CALCIUM METABOLISM IN RAT ISOLATED HEART MUSCLE AFTER ADRENALECTOMY

Mechanical performance and calcium metabolism were studied in isolated atria, obtained from adrenalectomized rats. Bilateral adrenalectomy was carried out one week before dissection of the atria. 1. Upon incubation in normal Tyrode solution for 3 h the contractile force of isolated atria obtained from adrenalectomized rats diminished significantly more rapidly than that of control atria. The effect was the same in spontaneously beating and in electrically driven atria (frequency 300/min). 2. Corticosterone (10-5 g/ml) dissolved in the medium completely prevented the accelerated decline in contraction amplitude, observed in isolated atria from adrenalectomized rats. 3. Approximately one week after bilateral adrenalectomy, the serum calcium content was significantly lower than that of control animals, although the calcium concentration in heart muscle remained unchanged. 4. The uptake of45Ca from the medium by isolated atria proved significantly slower after adrenalectomy. However, in both cases (control atria and organs from adrenalectomized rats) all of the cellular Ca was exchangeable. 5. Corticosterone (10-5 g/ml) in the medium restored the retarded uptake of45Ca after adrenalectomy to control values. 6. The changes in mechanical performance and in calcium metabolism, observed in isolated atrial tissue from adrenalectomized rats migh be caused by a reduced permeability of the cell membrane towards Ca. Also in vitro, corticosterone restored the membrane permeability to normal values. © 1969 Springer-Verlag.