AJP - Cell Physiology, Vol 235, Issue 5 199-C203, Copyright © 1978 by American Physiological Society
Relationship of intracellular creatine concentration and uptake to muscle mass in vivo
W. W. Hofmann, J. Butte and H. A. Leon
Attempts have been made to evaluate the role of intracellular creatine in
conditions leading to increased or decreased amounts of contractile protein
in rat skeletal muscles. Resting concentrations of intracellular creatine
([Cr]i) and creatine phosphate ([CrP]i) were compared in gastrocnemius and
soleus muscles with those immediately after a 20-s tetanic stimulation. The
hydrolysis of creatine phosphate was the same after heavily and lightly
loaded contractions, suggesting that hypertrophy of isometric exercise is
not mediated by creatine. With atrophy after denervation or interruption of
sciatic axoplasmic flow [Cr]i also remained unchanged, though [CrP]i and
the rate of Cr uptake fell after denervation. The major change in adult red
and white muscle bulk with unaltered [Cr]i suggests that the Cr sensitivity
found by others in developing muscle in vitro has been supplemented or
replaced by other control mechanisms.
