Abnormal Na channel gating in murine cardiac myocytes deficient in myotonic dystrophy protein kinase.

DMPK is a serine/threonine kinase implicated in the human disease myotonic muscular dystrophy (DM). Skeletal muscle Na channels exhibit late reopenings in Dmpk-deficient mice and peak current density is reduced, implicating DMPK in regulation of membrane excitability. Since complete heart block and sudden cardiac death occur in the disease, we tested the hypothesis that cardiac Na channels also exhibit abnormal gating in Dmpk-deficient mice.