Caffeine suppresses length dependency of Ca2+ sensitivity of skinned striated muscle.
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.
de Beer
E L
EL
Department of Medical Physiology, University of Utrecht, The Netherlands.
Gründeman
R L
RL
Wilhelm
A J
AJ
Caljouw
C J
CJ
Klepper
D
D
Schiereck
P
P
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008854:Microscopy, Electron; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D009200:Myocardial Contraction / Q000187:drug effects; D011817:Rabbits; D016276:Ventricular Function
D002110:Caffeine; D002118:Calcium