Inhibition of aftercontractions and phasic calcium release by yohimbine in ferret papillary muscle.
Phasic release of calcium from the sarcoplasmic reticulum occurs in all mammalian cardiac preparations when the intracellular calcium concentration is sufficiently high. The phasic calcium release is often sufficient to trigger electrophysiological responses and aftercontractions. These can be detrimental to normal cardiac function. We induced phasic calcium release in ferret papillary muscles loaded with the calcium indicator aequorin. Development of phasic calcium release was associated with an increase in resting and peak [Ca2+]i. Inhibiting sodium channels with yohimbine reduced resting [Ca2+]i and prevented phasic calcium release. We propose a mechanism where by reduced [Na+]i, and the subsequent increased efflux of calcium via sodium/calcium exchange reduced [Ca2+]i.
Briggs
G M
GM
Cardiovascular Division, Harvard Thorndike Laboratory, Beth Israel Hospital, Harvard Medical School, Boston, MA.
Morgan
J P
JP
Gwathmey
J K
JK
D000331:Aequorin / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005289:Ferrets; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000648:ultrastructure; D010210:Papillary Muscles / Q000187:drug effects; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D015016:Yohimbine / Q000494:pharmacology*
D015016:Yohimbine; D000331:Aequorin; D002118:Calcium