In vivo phosphorus 31 magnetic resonance spectroscopy of rat hind limb skeletal muscle during sepsis
D. O. Jacobs, J. Maris, R. Fried, R. G. Settle, R. R. Rolandelli, M. J. Koruda, B. Chance and J. L. Rombeau
Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia.
High-energy phosphate metabolism in skeletal muscle is altered during
sepsis, although the chronology of events is uncertain. Phosphorus 31
magnetic resonance spectroscopy was used to measure changes in muscle
energy stores of the left hind limb musculature of adult male rats during
sepsis. Following control scans, cecal ligation and puncture were performed
and scanning was repeated 6, 24, and 48 hours after surgery. The ratios of
phosphocreatine (PCr) to inorganic phosphate (Pi), a measure of energy
stores, and adenosine triphosphate (ATP) to Pi ratio, a measure of the
energy available for immediate use, were determined from peak heights.
Intracellular pH was calculated using the distance between Pi and PCr
peaks. In surviving animals, a 40% decrease in PCr/Pi ratio (+/- SEM) was
observed by 24 hours (22.3 +/- 3.0 at time 0 vs 13.3 +/- 2.8 at 24 hours),
whereas energy availability (beta-ATP/Pi) was statistically unchanged (18.2
+/- 2.2 at time 0 vs 15.2 +/- 1.2 at 48 hours). Intracellular pH did not
change. Both PCr/Pi and ATP/Pi ratios were inversely correlated with time.
In this model of documented peritonitis, skeletal muscle energy metabolism
is rapidly altered following severe infection, and these changes can be
detected using 31P magnetic resonance spectroscopy.