The Binding of Zinc to Glycerol‐extracted Muscle, and Its Relaxing Effect.

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Abstract
: The binding of zinc to glycerol‐extracted rabbit psoas muscle has been correlated with the zinc + ATP‐induced relaxation. The minimum amount of zinc that must be absorbed by the glycerol‐extracted fibres for complete isometric relaxation is about 3–4 mmoles per kg dry weight, which is close to the amount lost during glycerol‐extraction. The extracted fibres are able to absorb zinc in great excess of the concentration necessary for complete relaxation. The pH‐dependence of the contraction‐inhibiting effect of zinc and of the binding of zinc in high concentrations to the muscle shows that groups with a pK‐value of about 7, probably imidazole groups, are involved in both cases. The finding of an additive synergism between the effects of zinc and mersalyl suggests that also SH‐groups may be involved in the functionally relevant coupling of zinc to the contractile element.