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Abstract #4045

Water Exchange Kinetics in the Isolated Heart Correlate with Na+/K+ ATPase Activity: Potentially High Saptiotemporal Resolution in Vivo MR Access to Cellular Metabolic Actiivity

Yajie Zhang1, James A. Balschi1

1Medicine, Brigham and Women's Hospital, Boston, MA, United States

The extracellular relaxation agent, GdDTPA2- was used to distinguish intra- and extracellular 1H2O signals by altering their T1 values. Equilibrium trans-plasma membrane water exchange kinetics were quantified using two-site-exchange analysis to obtain the mean intracellular water life time (i ). Our studies found that i-1 (water exchange) correlated with Na+/K+ ATPase activity in isolated perfused rat hearts. Thus, i-1 acts as a biomarker for the cellular membrane transport activity. Potentially i-1 is altered in pathological states. i can be determined from pharmacokinetic analyses of in vivo 1H2O DCE-MRI studies. These findings could enable high resolution functional metabolic imaging.