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EDTA relaxation of glycerol-treated muscle fibers, and the effects of magnesium, calcium and manganese ions

1957; Elsevier BV; Volume: 68; Issue: 1 Linguagem: Inglês

10.1016/0003-9861(57)90329-6

1096-0384

Shizuo WATANABE, W. W. Sleator,

Pharmacological Effects and Assays

The relaxing effects of EDTA on glycerol-treated muscle fibers were studied quantitatively in the presence of Mg++, Ca++, and Mn++ in various combinations. These conclusions were drawn: 1. All of the three substances EDTA, Mg++, and ATP must be present to produce relaxation of well-washed fibers. 2. The effective concentration of EDTA depends upon the concentration of Mg++ present. 3. Enough Mg++ and EDTA remain on an EDTA-relaxed fiber after it has been washed up to 15 min. in 160 mM KCl to exert a measurable effect. 4. In the initial contraction, Mn++ can take the place of Mg++, but Ca++ cannot. 5. EDTA relaxation can be reversed by both Ca++ and Mn++, but more Mn++ is required. 6. Neither Mn++ nor Ca++ can take the place of Mg++ in the EDTA relaxation process. 7. ITP cannot replace ATP in the relaxation process though it can in contraction. 8. PDTA is as effective as EDTA in relaxing fibers. 9. The relaxing effect of EDTA decreases as pH increases, and has nearly vanished at pH 8. 10. An explanation of some of the above results in terms of a “four species” complex of ATP, Mg++, EDTA, and the contractile protein is discussed.