Spontaneous and electrically evoked Ca2+ transients in cardiomyocytes of the rat pulmonary vein.
The pulmonary vein is surrounded by an external sleeve of cardiomyocytes that are widely recognised to play an important role in atrial fibrillation. While intracellular Ca(2+) is thought to influence the electrical activity of cardiomyocytes, there have been relatively few studies examining Ca(2+) signalling in these cells. Therefore, using fluo-4 and fluorescence imaging microscopy, we have investigated Ca(2+) signalling in an intact section of the rat pulmonary vein. Under resting conditions cardiomyocytes displayed spontaneous Ca(2+) transients, which were variable in amplitude and had a frequency of 1.6±0.03Hz. The Ca(2+) transients were asynchronous amongst neighbouring cardiomyocytes and tended to propagate throughout the cell as a wave. Removing extracellular Ca(2+) produced a slight reduction in the amplitude and frequency of the spontaneous Ca(2+) transients; however, ryanodine (20μM) had a much greater effect on the amplitude and reduced the frequency by 94±2%. Blocking IP(3) receptors with 2-aminoethoxydiphenyl borate (20μM) also reduced the amplitude and frequency (by 73±11%) of these events, indicating the importance of Ca(2+) release from the SR. Electrical field stimulation of the pulmonary vein produced Ca(2+) transients in cardiomyocytes that were significantly reduced by either voltage-gated Ca(2+) channel blockers or ryanodine.
Logantha
Sunil Jit R J
SJ
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom.
Cruickshank
Stuart F
SF
Rowan
Edward G
EG
Drummond
Robert M
RM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology*; D006325:Heart Atria / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000502:physiology; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D011667:Pulmonary Veins / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology
D002121:Calcium Channel Blockers; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium