Determination of Ca²⁺-release from the Isolated Smooth Muscle Cells in Suspension from the Guinea-pig Ileu

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Uruno, T., Watanabe, A., Takahashi, K., Sunagane, N., Matsuoka, Y. and Kubota, K. Determination of Ca²⁺ -release from the isolated smooth muscle cells in suspension from the guinea-pig ileum. Japanese Journal Smooth Muscle Research, 23 (2), 103-114, 1987-Collagenase-dispersed cells from the guinea-pig ileum were prepared and Ca²⁺ release into Ca²⁺-depleted solution from the isolated single cells obtained by the centrifugation of the dispersed cells on isotonic sucrose solution was determined with a Ca²⁺-selective electrode. A technique employing an isotonic sucrose solution for washing isolated cells permitted removal of contaminating extracellular fluids and obtaining the isolated cells with minimum loss of cellular Ca²⁺. The release of Ca²⁺ from the dispersed cells consisted of at least two phases. The Ca²⁺ release into an isotonic sucrose-Tris solution (ISTS) was significantly reduced and the early phase of the Ca²⁺ release disappeared. At 16°C, Ca²⁺ release depended on the composition of the bathing solution in a Ca²⁺-free salt solution, the later phase of Ca²⁺-release was abolished whereas in ISTS both phases disappeared. Furthermore, Ca²⁺ release was significantly reduced after the treatment of the dispersed cells with dispase (1, 500 units/ml) for 10 min. These results show that Ca²⁺ release into Ca²⁺-depleted solution from the isolated ileal cells with minimum loss of cellular Ca²⁺ show a biphasic curve and suggest that Ca²⁺ sources responsible for these phases may be of distinct origin.