Enhancement of K+ conductance improves in vitro the contraction force of skeletal muscle in hypokalemic periodic paralysis

An abnormal ratio between Na+ and K+ conductances seems to be the
cause for the depolarization and paralysis of skeletal muscle in
primary hypokalemic periodic paralysis. Recently we have shown that
the k+ channel opener cromakalim hyperpolarizes mammalian skeletal
muscle fibers. Now we have studied the effects of this drug on the
twitch force of muscle biopsies from normal and diseased human
skeletal muscle. Cromakalim had little effect on the twitch force
of normal muscle whereas it strongly improved the contraction force
of fibers from patients suffering from hypokalemic periodic
paralysis. Recordings of intracellular K+ and Cl- activities in
human muscle and isolated rat soleus muscle support the view that
cromakalim enhances the membrane K+ conductance (gK+). These data
indicate that K+ channel openers may have a beneficial effect in
primary hypokalemic periodic paralysis.