Membrane potentials and contractile events of hypertrophied rat cardia muscle.

Abstract

AbstractPrevious studies indicate that cardiac hypertrophy is associated with altered mechanical properties including prolonged contraction times and mechanical refractory periods and exaggerated aftercontractions in isolated rat papillary muscle preparations. The present study was designed to ascertain whether changes in transmembrane potentials accompany the altered mechanical properties. Responses of papillary muscles from hypertrophied hearts of deoxycorticosterone acetate-treated Wistar Kyoto (WKY) rats were compared to those of nonhypertrophied, sham-treated WKYs. Muscles connected to a force transducer in a bathing chamber containing a 27° oxygenated physiological salt solution were subjected to field stimulation and isometric tension measured. Intracellular microelectrodes were used to measure transmembrane potentials of single impaled cells. When compared to nonhypertrophied controls, the hypertrophied preparations had (1) longer action potentials and contraction times, (2) longer electrical and ...