Journal of Applied Physiology, Vol 73, Issue 1 82-87, Copyright © 1992 by American Physiological Society
Effects of hyperphosphatemia on diaphragmatic strength and endurance
H. Bark, M. Nizri, A. Tarasuik and D. Heimer
Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rechovot, Israel.
Effects of an infusion of Na2HPO4 on diaphragm strength, endurance, and
magnitude of recovery were evaluated in in situ canine diaphragm strips.
Results showed no effect on maximal isometric tetanic tension. Twitch
tension and tension in the low- (10-Hz) frequency range were significantly
increased (P less than 0.01). Time to fatigue (endurance) increased by 38
+/- 4.5% in the group that received phosphorus compared with its control
and decreased by 18.5 +/- 2.5% in the group that received dextrose compared
with its control (P less than 0.005). Recovery from fatigue was also
significantly improved after the phosphorus infusion. Serum ATP and
2,3-diphosphoglycerate levels were unchanged throughout the experiment. The
results of this study support the notion that hyperphosphatemia improves
diaphragmatic endurance and recovery from fatigue. The mechanisms involved
may in part be due to the phosphate-buffering effects, which limit the
extent of the muscle intracellular acidosis produced with fatigue.
