Na+/Ca2+ exchange activity is increased in Alzheimer's disease brain tissues.
These studies were performed to determine the changes that occur in Na+/Ca2+ exchange activity in Alzheimer's disease (AD) brain tissues. Cerebral plasma membrane vesicles were purified by sucrose density gradient centrifugation from frozen postmortem hippocampal/temporal cortex tissue slices derived from age matched brains of normal, AD and non-Alzheimer dementia (NAD) origin (autopsy confirmed). Membrane marker assays (Na/K ATPase, muscarinic receptor, cytochrome c oxidase) revealed no change in membrane purity across different preparations. Thin-section electron microscopy revealed predominantly intact unilamellar vesicles. Vesicles were preincubated for 15 min (37 degrees C) in buffer containing 132 mM NaCl, 5 mM KCl, 1.3 mM MgCl2, 10 mM glucose and 10 mM HEPES (pH 7.4). Ca2+ uptake was initiated by diluting vesicles 20-fold with buffer containing either 132 mM NaCl or 132 mM choline chloride and 45CaCl2 then terminated by addition of 200 microM LaCl3 and rapid filtration. Ca2+ content increased rapidly at first and then maintained a steady plateau for up to 5 min. When the Ca2+ ionophore A23187 (10 microM) with 100 microM EGTA was added after 4 min, Ca2+ content was reduced to 10% of its original value. Ruthenium red (10 microM) had no effect on Ca2+ content. Na(+)-dependent Ca2+ uptake (Ca2+ content measured in choline chloride minus that measured in NaCl) was increased in AD brains as evidenced by both an increase in the initial rise in Ca2+ content and in elevated values of peak plateau Ca2+ content.(ABSTRACT TRUNCATED AT 250 WORDS)
Colvin
R A
RA
Department of Zoological and Biomedical Sciences, Ohio University College of Osteopathic Medicine, Athens 45701.
Bennett
J W
JW
Colvin
S L
SL
Allen
R A
RA
Martinez
J
J
Miner
G D
GD
D000328:Adult; D000368:Aged; D000375:Aging; D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D001921:Brain / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003576:Electron Transport Complex IV / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008854:Microscopy, Electron; D008970:Molecular Weight; D010042:Ouabain / Q000378:metabolism; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D012016:Reference Values; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D019831:Sodium-Calcium Exchanger; D010042:Ouabain; D011813:Quinuclidinyl Benzilate; D012964:Sodium; D003576:Electron Transport Complex IV; D002118:Calcium