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31 P NMR studies of ATP concentrations and P i –ATP exchange in the rat kidney in Vivo : Effects of inhibiting and stimulating renal metabolism
Author(s) -
Shine Nancy,
Xuan Ai,
Weiner Michael W.
Publication year - 1990
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910140304
Subject(s) - chemistry , fructose , kidney , metabolism , dinitrophenol , cyanide , biophysics , biochemistry , medicine , endocrinology , biology , inorganic chemistry
Previous investigators found that cyanide (CN − ) is a potent inhibitor of renal Na + transport, while the uncoupling agent 2,4‐dinitrophenol (DNP) and fructose (both which lower ATP levels) are weak transport inhibitors. To examine the disparate effects of these substances measurements of ATP were performed, using 31 P NMR, while simultaneously monitoring renal Na + transport. Infusion of CN − , DNP, and fructose lowered whole kidney ATP levels by about the same extent (30%) while only CN − inhibited Na + transport. This may be due to the fact that CN − has a potent action on the thick ascending limb of Henle, while fructose and DNP may have a more proximal action. Alternatively, ATP turnover may be a more important determinant of transport than ATP concentrations. Saturation transfer experiments were performed to measure P i –ATP flux. Unilateral nephrectomy, high protein feeding, and methylprednisolone were used to stimulate metabolism and transport. The rate of P i ‐ATP flux was 20.1 μmol/min/g. However, because oxygen consumption was stimulated, the ATP/O ratio was 0.85, considerably less than the theoretical value of 3. Finally, atrial natriuretic factor, which increased Na + transport, had no effect on P i ‐ATP flux. The results raise the possibility that the saturation transfer technique does not detect all P i ‐ATP flux, especially when renal metabolism is Stimulated. © 1990 Academic Press, Inc.