AJP - Cell Physiology, Vol 254, Issue 4 C491-C497, Copyright © 1988 by American Physiological Society
Caffeine suppresses length dependency of Ca2+ sensitivity of skinned striated muscle
E. L. de Beer, R. L. Grundeman, A. J. Wilhelm, C. J. Caljouw, D. Klepper and P. Schiereck
Department of Medical Physiology, University of Utrecht, The Netherlands.
Freeze-dried skinned cardiac and skeletal muscle preparations of the rabbit
were immersed in Ca2+-containing solutions with different concentrations of
caffeine. The relation between the negative logarithm of the Ca2+
concentration (pCa) and normalized developed force was studied. The exact
position of these Ca2+-sensitivity functions proved to be dependent on both
the sarcomere length (monitored by means of laser diffraction) and caffeine
concentration. High concentrations of caffeine induce a reversible fall in
tension, particularly at low binding site saturation (low pCa) and long
sarcomere lengths. At a concentration of 10 mM caffeine, the sarcomere
length dependency of the Ca2+-sensitivity curves is markedly reduced for
the rising part of the curve. Only the depressive effect of caffeine at
high pCa remains. A possible mechanism of caffeine action is discussed.
