Caffeine-induced calcium release from sarcoplasmic reticulum of a skeletal muscle.

Ca efflux from sarcoplasmic reticulum (SR) of a skinned skeletal muscle fiber was measured quantitatively using 45Ca. The time course of Ca efflux was fitted by superimposing two exponential curves. Caffeine caused Ca efflux from SR at very low concentration of free Ca ion. In order to study the relation of the Ca efflux mechanism to Ca-induced Ca release, caffeine was introduced to SR under controlled free Ca concentration. The results showed that caffeine induced Ca release from SR.