title: Inositol 1,4,5-trisphosphate- and caffeine-sensitive Ca(2+)-storing organelle in bovine adrenal chromaffin cells.
abstract: The uptake and release properties of Ca2+ by several subcellular fractions of the bovine adrenal medulla were investigated. Investigation by the 45Ca2+ tracer method showed that permeabilized cells and the fractions of mitochondria (MT) and microsomes (MC) caused ATP-dependent Ca2+ uptake in a Ca2+ concentration-dependent manner (pCa 8-4), whereas permeabilized cells and the fractions of secretory granules (SG) were able to accumulate a significant amount of Ca2+ even in the absence of ATP, which was completed by the addition of hexokinase and glucose. In these organelle fractions, Ca2+ uptake in the presence of ATP at pCa 7 and pCa 5.8 was well-correlated with the activity of the NADPH cytochrome c reductase (marker enzyme for the endoplasmic reticulum) and cytochrome c oxidase (marker enzyme for mitochondria), respectively. As detected by Fura-2 ratiometry, both inositol 1,4,5-trisphosphate (IP3) and caffeine caused concentration-dependent Ca2+ releases from permeabilized cells and MC, but not from MT and SG. In an ATP-depleted condition, homogenates still took up a significant amount of Ca2+ but was not able to respond to IP3 and caffeine. These results suggest that the endoplasmic reticulum is a major Ca(2+)-storing organelle, which releases Ca2+ in response to IP3 and caffeine in bovine adrenal chromaffin cells.
authors.affiliation: Department of Toxicology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Teraoka
authors.forename: R
authors.initials: R
authors.lastname: Takai
authors.forename: T
authors.initials: T
authors.lastname: Taneike
authors.forename: T
authors.initials: T
authors.lastname: Hiraga
authors.forename: A
authors.initials: A
authors.lastname: Ohga
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002417:Cattle; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D007293:Inosine Triphosphate / Q000494:pharmacology*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D015388:Organelles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011506:Proteins / Q000378:metabolism
chemical_list: D010726:Phosphodiesterase Inhibitors; D011506:Proteins; D007293:Inosine Triphosphate; D002110:Caffeine