Induction of DNA breaks in cardiac myoblast cells by norepinephrine

We measured DNA single strand breaks (SSB) in cardiac myoblast cells in response to norepinephrine (NE) stimulation. Rat cardiac myoblast cells (H9c2) were stimulated with concentrations of 100 microMs to 1 mM NE for 2, 3, 4, and 12 hours after prior incubation with control solution, bunazosin, propranolol, verapamil, or captopril for 30 min. The DNA damage was measured by fluorometric alkaline elution. The strand scission factor, an index of the severity of SSB, increased slightly after stimulation with 200 microMs NE for 12 hours and with 1 mM NE for 4 hours. This increase was prevented by catalase or superoxide dismutase, which prevent production or accumulation of active oxygen radicals, during the stimulation, but not by pretreatment with a alpha-receptor antagonist, a beta-adrenergic receptor antagonist, a Ca2+ antagonist, or an angiotensin converting enzyme inhibitor. Thus, DNA SSB were induced by NE in cardiac myoblast cells. Certain active oxygen species may contribute to the DNA damage induced by NE.