ABSTRACT
1. The effect of digoxin on calcium transport across muscle strips isolated from rat diaphragms was investigated. 2. Digoxin at concentrations ranging between 0.2-5.0 ng/ml in the incubation solution increased significantly (P less than 0.5) intracellular calcium in the diaphragm muscle strips in a dose-dependent pattern. 3. The inclusion of digoxin (2 ng/ml) and aminophylline (18.75 micrograms/ml) in the incubation medium showed a significant increase (P less than 0.001) in calcium uptake suggesting a synergistic effect on intracellular calcium accumulation. 4. The presence of digoxin with verapamil in the incubation medium showed a partial alleviation of the inhibitory effect of verapamil on calcium transport. 5. The effect of increasing calcium concentration in the presence of digoxin and digoxin plus aminophylline in the incubation medium, showed a nonsaturable linear relationship between calcium concentration and intracellular calcium accumulation.
