Interaction of Ca, Mg and ATP in glycerinated taenia coli of guinea pig.

Ca sensitivity and energy dependence in the contractile proteins of the glycerinated taenia coli of guinea pig were studied. Above 1 X 10(-7)M Ca caused contraction in muscle which had been immersed in glycerol solution for 7 days in the presence of 5 mM Mg-ATP. Muscles which had been immersed in glycerol for 30 days had a higher Ca sensitivity than ones in glycerol for 7 days. When AMP or ADP (5, 10 MM) in place of ATP was added in the presence of 1 X 10(-6) M Ca and Mg(5, 10 mM), there was no contraction. Increasing the concentration of the same molar ratio of Mg-ATP from 1 to 20 mM in the presence of 1 X 10(-6) M Ca, the tension increased according to the Mg-ATP concentration. However, increase in Mg or ATP only in the presence of 1 X 10(-6) M Ca did not increase the tension. In conclusion, the three factors of Ca, Mg and ATP are essential for the activation of the contractile elements of glycerinated taenia. It is also suggested that the tension development in glycerinated taemia is controlled by the concentration of Ca and Mg-ATP complexes in intracellular fluid.