External Ca2+-dependent Ca2+ release in directly stimulated diaphragm muscles of mice.

Intracellular Ca2+ release in directly stimulated diaphragm muscles of mice was found to be dependent on external Ca2+, using the intracellular Ca2+ aequorin luminescence transient technique. The Ca2+ mobilization into the cells may operate via a voltage- and external Ca2+-dependent mechanism, and via a caffeine- and external Ca2+-independent one, from the Ca2+ pools in plasma membranes or in the terminal cisternae of sarcoplasmic reticulum.