Evidence for extracellular localization of activator calcium in dog coronary artery smooth muscle as studied by the pyroantimonate method

Cell and Tissue Research
S Suzuki, H Sugi

Abstract

Correlated physiological and electron-microscopic studies were made on the source of calcium activating the contractile system (activator calcium) in dog coronary artery smooth muscle fibers. The magnitude of contracture tension induced by 100 mM K+ was dependent on external Ca2+ concentration and reduced or eliminated by factors known to reduce the Ca2+ spike or Ca2+ influx. Little or no mechanical response was elicited by treatments known to cause release of intracellularly stored calcium. These results indicated that the contractile system is mainly activated by the inward movement of extracellular calcium. In accordance with the physiological experiments, electronopaque pyroantimonate precipitate containing calcium was found in the lumina of caveolae, but not in any intracellular structures close to the plasma membrane, when the relaxed fibers were fixed in a 1% osmium tetroxide solution containing 2% potassium pyroantimonate. If the contracted fibers were fixed in the same solution, the pyroantimonate precipitate was diffusely distributed in the myoplasm in the form of numerous particles, while the precipitate in the caveolar lumina was scarcely seen. These findings are discussed in connection with the regulation of intrac...Continue Reading

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Citations

Dec 1, 1993·Proceedings of the National Academy of Sciences of the United States of America·R G Anderson
Mar 1, 1993·The Journal of Cell Biology·T Fujimoto
Jun 6, 1998·Proceedings of the National Academy of Sciences of the United States of America·M IsshikiA Kamiya
Dec 29, 2011·Frontiers in Bioscience (Landmark Edition)·Biswaranjan PaniBrij B Singh
Mar 28, 2009·Cell Calcium·Biswaranjan Pani, Brij B Singh
Aug 15, 2002·The Journal of Biological Chemistry·Masashi IsshikiRichard G W Anderson

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