Energetics of sodium transport in the kidney

Compartmentation of Nucleotides in Corn Root Tips Studied by 31P-NMR and HPLC

“…4). Qualitatively similar results have been reported from NMR studies of human blood platelets (4,28), skeletal muscle (7), and rat kidney (6), where it was concluded that NMR-invisible nucleotides present in vivo were immobilized; immobilized species give broad signals that are undetectable in high resolution experiments. Hence, existence of an immobilized pool of NDP in corn root tips is one possible explanation for the result in Figure 4.…”

“…Any such distinctions between nucleotides in vivo is lost on extraction. Compartmentation of nucleotides between immobilized and freely mobile pools was suggested in NMR studies of human blood platelets (4,28), skeletal muscle (7), and rat kidney (6), from comparison of the amounts of nucleotides visible in vivo and in extracts. Such comparisons were made in this study, and our results indicate the existence of an NMR-invisible pool of NDP in vivo.…”

P-31 nuclear magnetic resonance spectroscopic study of obstructive uropathy in the rat.

“…Another observation is that the T. of Pi is significantly longer in ob- (36), it is possible that an indirect measurement of ATP turnover rate would be different between the two groups. More accurate measurement of the differences in energy turnover rates between obstructed and nonobstructed kidneys might be accomplished with P-3 1 NMR by using saturation transfer techniques that were not used in this study, but will be used for future work (22,37). The observation that phosphate derived from the urine does not resonate at the frequency observed for intracellular Pi may partially explain the differences in the concentration of kidney tissue Pi determined by in vivo P-31 NMR and the destructive chemical techniques that have been well described by other workers (4,22,(37)(38)(39).…”

“…More accurate measurement of the differences in energy turnover rates between obstructed and nonobstructed kidneys might be accomplished with P-3 1 NMR by using saturation transfer techniques that were not used in this study, but will be used for future work (22,37). The observation that phosphate derived from the urine does not resonate at the frequency observed for intracellular Pi may partially explain the differences in the concentration of kidney tissue Pi determined by in vivo P-31 NMR and the destructive chemical techniques that have been well described by other workers (4,22,(37)(38)(39). Explanations given to explain this phenomenon, which has been noted in other organs as well as kidney, include the rapid breakdown of other phosphate-containing compounds unavoidable with destructive techniques and the concept of most intracellular Pi being in a bound state and therefore not detectable by P-3 1 NMR, which measures more mobile chemical species.…”

Disorders of Plasma Phosphate and Indications for its Measurement

“…The total inorganic phosphate in cells is approximately 4-5 mmol/kg tissue water;' but 75--85% of this is thought to be bound, sequestrated in organelles or otherwise immobilized. Nuclear magnetic resonance studies show that the concentration of free inorganic phosphate within the cells is about I mmol/L, 10 Conditions that favour the binding of phosphate to organic compounds result in a shift of phosphate from the extracellular to the intracellular fluid and thereby causing hypophosphataemia (see later).…”