The Genetic Background of (NA+, K+)-ATPase a2 Knockout Mice Affects the Distribution of a2 and a3 Isoforms of This Enzyme in Brain and the Survival Time of Homozygous Newborns

Baran, A.M., T.M. Spranger, A.E. Moseley, J.B. Lingrel, and M.L. Caspers

The (Na+, K+)-ATPase maintains Na+ and K+ gradients in cells through the active transport of these ions across the plasma membrane. [3H]Ouabain, which binds with high affinity to the α-2 and α-3 isoforms of the (Na++K+)-ATPase, was used to study the distribution of these isoforms in the brains of adult wild type and heterozygous α-2 knockout mice of FVBN genetic background. Frozen, coronal brain sections (24 micron) were prepared and were assayed in a 100 mM Tris-HCl buffer containing 10 mM NaCl, 10 mM MgCl2, 5 mM ATP and 29 nM [3H]ouabain. The sections were exposed to Kodak BioMax Scientific Imaging film and the images were subjected to computer-assisted densitometry. In α-2 heterozygotes, significant decreases in the relative density of [3H]ouabain binding sites were observed in the cerebral cortex (5.1%) and hippocampus (4.4%) compared to wild-type mice. These findings are similar to results obtained with C57BL6 mice where small decreases in [3H]ouabain binding sites were observed in the cerebral cortex, hippocampus and thalamus of heterozygous α-2 knockout mice but are dissimilar to results using α-2 heterozygous 129/Black Swiss (mixed) mice where larger decreases in [3H]ouabain binding, relative to wild-type animals, were seen in all brain regions tested (Program #517.10, 2004 Abstract Viewer/Itinerary Planner, Washington, DC: Society for Neuroscience, CD-ROM). Strain differences also are seen in the survival time of homozygous α-2 knockout mice; FVBN knockout mice live approximately 1 day whereas the mixed and C57BL6 knockout mice die at birth. (Supported by NIH grants HL28573 and HL66062 and a gift from J.D. Rose.)

 

Presented at the 2005 Society for Neuroscience meeting, Washington, D.C. and 2007 spring American Chemical Society meeting, Chicago, IL.