CONTRACTION OF RAT UTERINE SMOOTH MUSCLE IN CA-FREE HIGH K SOLUTION

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Abstract
An intracellular Ca store was studied by recording isometric tension development of a thin bundle of the rat longitudinal uterine muscle produced by chemicals in a solution containing 4 mM EGTA [ethylene glycol-bis [.beta.-aminoethylether]-N,N''-tetraacetic acid]. This muscle was considered to have an intracellular Ca store. Caffeine did not induce contraction in Ca-free high K (G4) solution, but did cause a decrease of the Ca in this store. This effect of caffeine was blocked by procaine. At least some part of the intracellular Ca store in the rat uterine longitudinal muscle apparently has the same pharmacological characteristics as the sarcoplasmic reticulum of skeletal, cardiac, and tenia caeci smooth muscle.