title: Evaluation of extra- and intracellular apparent diffusion coefficient of sodium in rat skeletal muscle: effects of prolonged ischemia.
abstract: The mechanism of water and sodium apparent diffusion coefficient (ADC) changes in rat skeletal muscle during global ischemia was examined by in vivo 1H and 23Na magnetic resonance spectroscopy (MRS). The ADCs of Na+ and water are expected to have similar characteristics because sodium is present as an aqua-cation in tissue. The shift reagent, TmDOTP5(-), was used to separate intra- and extracellular sodium (Na+i and Na+e, respectively) signals. Water, total tissue sodium (Na+t), Na+i, and Na+e ADCs were measured before and 1, 2, 3, and 4 hr after ischemia. Contrary to the general perception, Na+i and Na+e ADCs were identical before ischemia. Thus, ischemia-induced changes in Na+e ADC cannot be explained by a simple change in the size of relative intracellular or extracellular space. Na+t and Na+e ADCs decreased after 2-4 hr of ischemia, while water and Na+i ADC remained unchanged. The correlation between Na+t and Na+e ADCs was observed because of high Na+e concentration. Similarly, the correlation between water and Na+i ADCs was observed because cells occupy 80% of the tissue space in the skeletal muscle. Ischemia also caused an increase in the Na+i and an equal decrease in Na+e signal intensity due to cessation of Na+/K+-ATPase function.
authors.affiliation: Department of Radiology, Indiana University, Indianapolis, Indiana 46202-5181, USA. ababsky@iupui.edu
authors.forename: Andriy M
authors.initials: AM
authors.lastname: Babsky
authors.forename: Stephen
authors.initials: S
authors.lastname: Topper
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Gao
authors.forename: Judy R
authors.initials: JR
authors.lastname: James
authors.forename: Shahryar K
authors.initials: SK
authors.lastname: Hekmatyar
authors.forename: Navin
authors.initials: N
authors.lastname: Bansal
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism; D004058:Diffusion; D005110:Extracellular Space / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D007511:Ischemia; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D010080:Oxazoles; D019047:Phantoms, Imaging; D011744:Pyrimidinones; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
chemical_list: D010080:Oxazoles; D011744:Pyrimidinones; C063359:2,3-dihydro-5H-oxazolo(3,2-a)thieno(3,2-d)pyrimidin-5-one; D012964:Sodium