title: Elevation of mitochondrial calcium by ryanodine-sensitive calcium-induced calcium release.
abstract: Calcium is an important regulator of mitochondrial function. Since there can be tight coupling between inositol 1,4, 5-trisphosphate-sensitive Ca(2+) release and elevation of mitochondrial calcium concentration, we have investigated whether a similar relationship exists between the release of Ca(2+) from the ryanodine receptor and the elevation of mitochondrial Ca(2+). Perfusion of permeabilized A10 cells with inositol 1,4, 5-trisphosphate resulted in a large transient elevation of mitochondrial Ca(2+) to about 8 microm. The response was inhibited by heparin but not ryanodine. Perfusion of the cells with Ca(2+) buffers in excess of 1 microm leads to large increases in mitochondrial Ca(2+) that are much greater than the perfused Ca(2+). These increases, which average around 10 microm, are enhanced by caffeine and inhibited by ryanodine and depletion of the intracellular stores with either orthovanadate or thapsigargin. We conclude that Ca(2+)-induced Ca(2+) release at the ryanodine receptor generates microdomains of elevated Ca(2+) that are sensed by adjacent mitochondria. In addition to ryanodine-sensitive stores acting as a source of Ca(2+), Ca(2+)-induced Ca(2+) release is required to generate efficient elevation of mitochondrial Ca(2+).
authors.affiliation: Department of Human Anatomy and Cell Biology, University of Liverpool, New Medical School, Ashton Street, Liverpool L69 3GE, United Kingdom. awms@liv.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: Nassar
authors.forename: A W
authors.initials: AW
authors.lastname: Simpson
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002463:Cell Membrane Permeability; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel; D014667:Vasopressins; D012433:Ryanodine; D002110:Caffeine; D014638:Vanadates; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium