title: Spontaneous and electrically evoked Ca2+ transients in cardiomyocytes of the rat pulmonary vein.
abstract: 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.
authors.affiliation: Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom.
authors.forename: Sunil Jit R J
authors.initials: SJ
authors.lastname: Logantha
authors.forename: Stuart F
authors.initials: SF
authors.lastname: Cruickshank
authors.forename: Edward G
authors.initials: EG
authors.lastname: Rowan
authors.forename: Robert M
authors.initials: RM
authors.lastname: Drummond
mesh_terms: 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
chemical_list: D002121:Calcium Channel Blockers; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium