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6-Fluoropyridoxol (6-FPOL) was evaluated as a simultaneous indicator of intracellular and extracellular pH and, hence, pH gradient in perfused rat hearts. After infusion, 19F NMR spectra rapidly showed two well-resolved peaks assigned to the intracellular and extracellular compartments, and pH was calculated on the basis of chemical shift with respect to a sodium trifluoroacetate standard. To demonstrate use of this molecule, dynamic changes in myocardial pH were assessed with a time resolution of 2 min during respiratory and metabolic alkalosis or acidosis and ischemia. For a typical heart, intracellular pH (pHi) = 7.14+/-0.01 and extracellular pH (pHe) = 7.52+/-0.02. In response to metabolic alkalosis, pHi remained relatively constant and the pH gradient increased. In contrast, respiratory challenge caused a significant increase in pHi. Independent measurements using pH electrodes and 31P NMR confirmed validity of the 19F NMR results.

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Abstract6-Fluoropyridoxol was evaluated as an intracellular pH indicator. This molecule exhibits exceptional sensitivity to changes in pH (-IO ppm acid/base shift) and a pK, -8.2 appropriate for physiological investigations. Using 19F NMR spectroscopy we determined both intra-and extracellular pH in whole blood and confirmed the measurements using traditional techniques: ion-electrodes and "P NMR spectroscopy.

Fluorinated proteins have been synthesized and characterized as potential in vivo 19F magnetic resonance imaging (MRI) and spectroscopy (MRS) agents. Proteins labeled with fluorine include bovine serum albumin, gamma-globulin, and purified immunoglobulin (IgG). The amino groups in proteins were selectively trifluoroacetylated using S-ethyl trifluorothioacetate to synthesize fluorinated proteins (TFA-protein; 1-3). In another approach, trifluoroacetamidosuccinic anhydride has been used to prepare corresponding fluorinated derivatives of proteins (TFASA-protein; 4-6). The fluorinated proteins have been purified by exhaustive dialysis and isolated in good yields (55-76%). The fluorinated proteins exhibit useful NMR characteristics and the biocompatibility for in vivo studies. The initial investigations demonstrate the potential of these new fluorinated proteins as in vivo MRI/MRS probes.