Figure 1. CPZ decreases K⁺-dependent Na⁺, K⁺-ATPase transport activity.

A. Raw trace of the effects of 30 µM of CPZ on Na⁺, K⁺-ATPase I_p in adult rat cardiac myocytes. The horizontal bold lines indicate the addition and wash-off of 5 mM KCl or the addition of CPZ, as indicated. B. Steady state current obtained following 5 and 10 min incubation with CPZ, compared to controls not treated with CPZ. C. Changes in K⁺-independent I_p following the addition of CPZ. D. The CPZ-induced changes of Na⁺, K⁺-ATPase I_p in adult rat cardiac myocytes are reversible. The data represent cells isolated from at least 6 individual animals, (number of cells shown inside bars; 1 min time point not shown) and are expressed as mean ±SEM (*significantly different from control, P<0.05). Differences between experimental groups were tested by one-way ANOVA followed by a Bonferroni post-hoc test in panel B and by unpaired t-test in panel C.