AJP - Cell Physiology, Vol 235, Issue 1 1-C7, Copyright © 1978 by American Physiological Society
Chemical energetics of single isometric tetani in mammalian smooth muscle
T. M. Butler, M. J. Siegman, S. U. Mooers and R. E. Davies
A rabbit taenia coli preparation has been used to study the chemical
energetics of smooth muscle contraction. Under the experimental conditions,
the muscle had no spontaneous mechanical activity, but could be fully
activated with the use of electrical field stimulation. ATP resynthesis
from glycolysis and respiration was stopped with a procedure that involved
treatment with metabolic inhibitors at 5 degrees C followed by rewarming to
18 degrees C. This procedure did not alter the high-energy phosphate
contents of mechanical responses of the muscle. Use of this preparation to
determine ATP and phosphorylcreatine changes during isometric tetani at 18
degrees C and a length of 86% LO showed that there was net ATP breakdown
initially with no significant phosphorylcreatine splitting. This was
followed by an increase in the rate of phosphorylcreatine splitting with
net ATP synthesis. The average rate of total high-energy phosphate
utilization was about 0.01 mumol/g.s for up to 60 s or about 150 times less
than that of frog sartorius at the same temperature.
