Measurement and modeling of Ca2+ waves in isolated rabbit ventricular cardiomyocytes.
The time course and magnitude of the Ca(2+) fluxes underlying spontaneous Ca(2+) waves in single permeabilized ventricular cardiomyocytes were derived from confocal Fluo-5F fluorescence signals. Peak flux rates via the sarcoplasmic reticulum (SR) release channel (RyR2) and the SR Ca(2+) ATPase (SERCA) were not constant across a range of cellular [Ca(2+)] values. The Ca(2+) affinity (K(mf)) and maximum turnover rate (V(max)) of SERCA and the peak permeability of the RyR2-mediated Ca(2+) release pathway increased at higher cellular [Ca(2+)] loads. This information was used to create a computational model of the Ca(2+) wave, which predicted the time course and frequency dependence of Ca(2+) waves over a range of cellular Ca(2+) loads. Incubation of cardiomyocytes with the Ca(2+) calmodulin (CaM) kinase inhibitor autocamtide-2-related inhibitory peptide (300 nM, 30 mins) significantly reduced the frequency of the Ca(2+) waves at high Ca(2+) loads. Analysis of the Ca(2+) fluxes suggests that inhibition of CaM kinase prevented the increases in SERCA V(max) and peak RyR2 release flux observed at high cellular [Ca(2+)]. These data support the view that modification of activity of SERCA and RyR2 via a CaM kinase sensitive process occurs at higher cellular Ca(2+) loads to increase the maximum frequency of spontaneous Ca(2+) waves.
MacQuaide
N
N
Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
Dempster
J
J
Smith
G L
GL
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D003198:Computer Simulation; D005456:Fluorescent Dyes / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D032342:Muscle Cells / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism
D002147:Calmodulin; D005456:Fluorescent Dyes; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium