C. Huchet et C. Leoty, SARCOPLASMIC-RETICULUM FUNCTION IN NEWBORN FERRET CREMASTER SKELETAL-MUSCLES, European journal of pharmacology, 271(1), 1994, pp. 141-149
A study of the properties of the sarcoplasmic reticulum was performed
with newborn ferret cremaster muscles at two different development sta
ges: at 8 and 21 days. The effects of extracellular Ca2+, caffeine and
cyclopiazonic acid, a specific sarcoplasmic reticulum Ca2+-ATPase inh
ibitor, were examined on intact cremaster skeletal muscles. The uptake
and release of Ca2+ were explored on saponin-skinned fibres with or w
ithout cyclopiazonic acid and some results obtained were compared with
those obtained with adult cremaster muscle. The results have shown th
at skeletal muscle sarcoplasmic reticulum of newborn animals possesses
the ability to accumulate and release Ca2+. Furthermore, application
of cyclopiazonic acid modified the twitch, the caffeine responses and
decreased the amount of Ca2+ taken up by the sarcoplasmic reticulum in
saponin-skinned fibres. In contrast to adult skeletal muscle, in newb
orn cremaster muscles, the Ca2+ dependence of the twitch suggests that
the Ca2+ influx at the sarcolemma level was mainly involved in the ac
tivation of the contraction. Furthermore, the results obtained in the
presence of cyclopiazonic acid were in favour, as in adult muscle, of
a participation of the sarcoplasmic reticulum in the relaxation proces
s.