Activation stabilization--further support for a new class of cardioactive substances.

Alinidine, a new compound with a bradycardic action, has a rate-decreasing and stabilizing action on the spontaneous contractions of single rat ventricular cardiac cells with a partially skinned and leaky sarcolemmal membrane but with a well-functioning sarcoplasmic reticulum. In the intact multicellular cat papillary muscle, alinidine delays the onset of mechanical activation at concentrations that hardly affect peak mechanical performance and the relaxation phase. From these results, we postulate that alinidine has a stabilizing action on activation, in particular on the release of calcium from the intracellular membranous system, with minimal effects on the total amount released and on the calcium reuptake or process of inactivation.