Heterogeneity of calcium stores and elementary release events in canine pulmonary arterial smooth muscle cells.
To examine the nature of inositol 1,4,5-trisphosphate (IP(3))-sensitive and ryanodine (Ryn)-sensitive Ca(2+) stores in isolated canine pulmonary arterial smooth cells (PASMC), agonist-induced changes in global intracellular Ca(2+) concentration ([Ca(2+)](i)) were measured using fura 2-AM fluorescence. Properties of elementary local Ca(2+) release events were characterized using fluo 3-AM or fluo 4-AM, in combination with confocal laser scanning microscopy. In PASMC, depletion of sarcoplasmic reticulum Ca(2+) stores with Ryn (300 microM) and caffeine (Caf; 10 mM) eliminated subsequent Caf-induced intracellular Ca(2+) transients but had little or no effect on the initial IP(3)-mediated intracellular Ca(2+) transient induced by ANG II (1 microM). Cyclopiazonic acid (CPA; 10 microM) abolished IP(3)-induced intracellular Ca(2+) transients but failed to attenuate the initial Caf-induced intracellular Ca(2+) transient. These results suggest that in canine PASMC, IP(3)-, and Ryn-sensitive Ca(2+) stores are organized into spatially distinct compartments while similar experiments in canine renal arterial smooth muscle cells (RASMC) reveal that these Ca(2+) stores are spatially conjoined. In PASMC, spontaneous local intracellular Ca(2+) transients sensitive to modulation by Caf and Ryn were detected, exhibiting spatial-temporal characteristics similar to those previously described for "Ca(2+) sparks" in cardiac and other types of smooth muscle cells. After depletion of Ryn-sensitive Ca(2+) stores, ANG II (8 nM) induced slow, sustained [Ca(2+)](i) increases originating at sites near the cell surface, which were abolished by depleting IP(3) stores. Discrete quantal-like events expected due to the coordinated opening of IP(3) receptor clusters ("Ca(2+) puffs") were not observed. These data provide new information regarding the functional properties and organization of intracellular Ca(2+) stores and elementary Ca(2+) release events in isolated PASMC.
Janiak
R
R
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA.
Wilson
S M
SM
Montague
S
S
Hume
J R
JR
D000804:Angiotensin II / Q000494:pharmacology; D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D005260:Female; D005456:Fluorescent Dyes / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects / Q000378:metabolism; D012077:Renal Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology; D014966:Xanthenes / Q000494:pharmacology
D000814:Aniline Compounds; D015220:Calcium Channels; C409648:Fluo 4; D005456:Fluorescent Dyes; D007211:Indoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; D014665:Vasodilator Agents; D014966:Xanthenes; D000804:Angiotensin II; D012433:Ryanodine; C059715:Fluo-3; D002110:Caffeine; D002118:Calcium; C000543:cyclopiazonic acid