Quantal Ca²⁺ mobilization by ryanodine receptors is due to all-or-none release from functionally discrete intracellular stores

Cheek, T. R.; Berridge, M. J.; Moreton, R. B.; Stauderman, K. A.; Murawsky, M. M. and Bootman, M. D. (1994). Quantal Ca²⁺ mobilization by ryanodine receptors is due to all-or-none release from functionally discrete intracellular stores. The Biochemical Journal, 301 pp. 879–883.

URL: http://www.biochemj.org/bj/301/bj3010879.htm

Abstract

Low caffeine concentrations were unable to completely release the caffeine- and ryanodine-sensitive intracellular Ca²⁺ pool in intact adrenal chromaffin cells. This 'quantal' Ca²⁺ release is the same as that previously observed with inositol Ins(1,4,5)P3-induced Ca²⁺ release. The molecular mechanism underlying quantal Ca²⁺ release from the ryanodine receptor was investigated using fura-2 imaging of single chromaffin cells. Our data indicate that the intracellular caffeine-sensitive Ca²⁺ pool is composed of functionally discrete stores, that possess heterogeneous sensitivities to caffeine. These stores are mobilized by caffeine in a concentration-dependent fashion, and, when stimulated, individual stores release their Ca²⁺ in an 'all-or-none' manner. Such quantal Ca²⁺ release may be responsible for graded Ca²⁺ responses in single cells.

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