Figure 4. Bumetanide was superior to acetazolamide in preventing decreases in force under low K⁺ conditions.

Sequential 2-mM K⁺ challenges were applied to soleus from heterozygous R669H^+/m female (left) or male (right) mice. In each trial, a pair of muscles from the same animal was tested in separate tissue baths. The control had no drug applied (gray) while the other muscle was pretreated with acetazolamide (ACTZ) (100 μM) (red) in the first low-K⁺ challenge and bumetanide (BMT) (0.5 μM) before the second challenge. The modest improvement with ACTZ was not significantly different from untreated (p > 0.3, n = 6). BMT prevented decreases in force in females, and substantially reduced such decreases in males (p < 0.01, n = 3).