C. Huchet et C. Leoty, EFFECTS OF CYCLOPIAZONIC ACID ON CA2-ACTIVATED TENSION PRODUCTION IN SKINNED SKELETAL-MUSCLE FIBERS OF THE FERRET(), European journal of pharmacology, 241(1), 1993, pp. 41-46
The effect of cyclopiazonic acid, an inhibitor of sarcoplasmic reticul
um Ca2+-ATPase, was investigated on force generation by the contractil
e apparatus in Triton-skinned fibres from extensor digitorum longus an
d soleus. Concentrations of cyclopiazonic acid lower than, 10 muM were
without effect on Ca2+-activated tension in both types of muscles. In
contrast, in soleus, cyclopiazonic acid (20, 50, 100 muM) was found t
o shift reversibly the relation-tension pCa (-log[Ca 2+]) towards lowe
r free Ca2+ and to decrease maximal Ca2+-activated tension, in a dose-
dependent manner. In extensor digitorum longus, the Ca2+ sensitivity w
as significantly increased only at a high cyclopiazonic acid concentra
tion (100 muM) and for all the concentrations tested between 5 to 100
muM maximal Ca2+-activated tension was unchanged. These results sugges
t that cyclopiazonic acid has a direct effect on contractile proteins,
in a dose-dependent manner. Ca2+ sensitivity and Ca2+-activated maxim
al tension of the contractile apparatus were differentially affected i
n fast- (extensor digitorum longus) and slow-twitch (soleus) fibres fr
om ferret skeletal muscle.