Effects of ouabain on Ca⁴⁵ entry in quiescent and electrically driven rabbit atria

¹ Department of Pharmacology, University of Mississippi Medical Center, Jackson, Mississippi

The effects of ouabain (4 x 10^–8 to 1 x 10^–6 m) on the rates of Ca⁴⁵ entry into quiescent and electrically driven rabbit atria have been compared. Ouabain had no effect on Ca⁴⁵ entry on quiescent preparations but increased the uptake in those electrically driven. The calculated entry per impulse was estimated to be 0.0027 pmole/cm² in controls and 0.0129 pmole/cm² in ouabain-treated preparations. It is concluded that digitalis glycosides only affect calcium exchange that accompanies the process of activation.