Calcium-dependent electrophysiological alterations in hypertrophied rat cardiomyocytes.
We compared the occurrence of calcium-dependent electrophysiological alterations in left ventricular myocytes isolated from the heart of old spontaneously hypertensive (SHR) and age-matched normotensive Wistar Kyoto rats (WKY). Electrical and mechanical activity were measured in patch-clamped myocytes in which intracellular Ca2+ was allowed to change freely. In parallel experiments, intracellular Ca2+ concentration was monitored in fura-2-AM preloaded cells using an image analysis system. Left ventricular myocytes from SHR showed a significantly greater membrane capacitance (an index of cell size), a prolonged duration of the action potential and a higher incidence of delayed afterdepolarization (DADs) and associated aftercontractions, and of spontaneous activity. DADs were likely generated by intracellular Ca2+ waves due to spontaneous and local Ca2+ release from intracellular stores. These results demonstrate that DADs, possibly related to spontaneous intracellular Ca2+ waves, occur frequently in hypertrophied rat cardiomyocytes and may be a relevant arrhythmogenic mechanism.
Ruocco
C
C
Department of Preclinical and Clinical Pharmacology, University of Florence, Italy.
Cerbai
E
E
Failli
P
P
Giotti
A
A
Mugelli
A
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006332:Cardiomegaly / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D008564:Membrane Potentials; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D002118:Calcium