title: Correlated sodium and potassium imbalances within the ischemic core in experimental stroke: a 23Na MRI and histochemical imaging study.
abstract: This study addresses the spatial relation between local Na(+) and K(+) imbalances in the ischemic core in a rat model of focal ischemic stroke. Quantitative [Na(+)] and [K(+)] brain maps were obtained by (23)Na MRI and histochemical K(+) staining, respectively, and calibrated by emission flame photometry of the micropunch brain samples. Stroke location was verified by diffusion MRI, by changes in tissue surface reflectivity and by immunohistochemistry with microtubule-associated protein 2 antibody. Na(+) and K(+) distribution within the ischemic core was inhomogeneous, with the maximum [Na(+)] increase and [K(+)] decrease typically observed in peripheral regions of the ischemic core. The pattern of the [K(+)] decrease matched the maximum rate of [Na(+)] increase ('slope'). Some residual mismatch between the sites of maximum Na(+) and K(+) imbalances was attributed to the different channels and pathways involved in transport of the two ions. A linear regression of the [Na(+)]br vs. [K(+)]br in the samples of ischemic brain indicates that for each K(+) equivalent leaving ischemic tissue, 0.8±0.1 Eq, on average, of Na(+) enter the tissue. Better understanding of the mechanistic link between the Na(+) influx and K(+) egress would validate the (23)Na MRI slope as a candidate biomarker and a complementary tool for assessing ischemic damage and treatment planning.
authors.affiliation: Department of Anesthesiology, Allegheny-Singer Research Institute, Pittsburgh, PA 15212, USA. vyushman@wpahs.org
authors.forename: Victor E
authors.initials: VE
authors.lastname: Yushmanov
authors.forename: Alexander
authors.initials: A
authors.lastname: Kharlamov
authors.forename: Boris
authors.initials: B
authors.lastname: Yanovski
authors.forename: George
authors.initials: G
authors.lastname: LaVerde
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Boada
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Jones
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000150:complications / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011188:Potassium / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000032:analysis / Q000378:metabolism*; D020521:Stroke / Q000209:etiology / Q000378:metabolism*
chemical_list: D012964:Sodium; D011188:Potassium
keywords: (23)Na MRI; 3D; ADC; BBB; Focal ischemia; MAP2; MCA, MCAO, MCAT; Permanent MCAO; RF; ROI; Rat brain; Tissue potassium; Tissue sodium; [Na(+)](br) and [K(+)](br); apparent diffusion coefficient; blood–brain barrier; brain tissue sodium and potassium concentration, respectively; microtubule-associated protein 2; middle cerebral artery, MCA occlusion, and MCA transection with bilateral common carotid artery occlusion, respectively; radiofrequency; region of interest; three-dimensional