title: Sarcoplasmic reticulum calcium load regulates rat arterial smooth muscle calcium sparks and transient K(Ca) currents.
abstract: The regulation of calcium (Ca(2+)) sparks and transient calcium-sensitive K(+) (K(Ca)) currents by acute changes in sarcoplasmic reticulum (SR) Ca(2+) load ([Ca(2+)](SR)) was investigated in rat cerebral artery smooth muscle cells using laser-scanning confocal microscopy in combination with patch clamp electrophysiology. [Ca(2+)](SR) was elevated by: (i) increasing the activity of the SR Ca(2+)-ATPase with an anti-phospholamban monoclonal antibody, or (ii) blocking Ca(2+) release from the SR with tetracaine, a membrane-permeant, reversible ryanodine-sensitive Ca(2+) release (RyR) channel blocker. Alternatively, [Ca(2+)](SR) was progressively decreased over time with a low concentration of thapsigargin (20 nM), a SR Ca(2+)-ATPase blocker. An elevation in [Ca(2+)](SR) increased Ca(2+) spark and transient K(Ca) current frequency, but did not alter the amplitude, decay or spatial spread of Ca(2+) sparks or the coupling ratio or amplitude correlation between Ca(2+) sparks and evoked transient K(Ca) currents. Decreasing [Ca(2+)](SR) reduced Ca(2+) spark frequency, amplitude and spatial spread and this reduced transient K(Ca) current frequency and amplitude. However, even when mean Ca(2+) spark amplitude and spread decreased by up to 47 and 56 % of control, respectively, the coupling ratio or amplitude correlation between Ca(2+) sparks and transient K(Ca) currents was not affected. These data demonstrate that acute changes in [Ca(2+)](SR) regulate Ca(2+) sparks and transient K(Ca) currents in arterial smooth muscle cells.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000276:immunology; D002536:Cerebral Arteries / Q000378:metabolism*; D004553:Electric Conductivity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013748:Tetracaine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014018:Tissue Distribution / Q000187:drug effects; D000099211:Phospholamban
chemical_list: D000911:Antibodies, Monoclonal; D002118:Calcium; D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D015221:Potassium Channels; D013748:Tetracaine; D019284:Thapsigargin; D000099211:Phospholamban