A novel form of host defence: membrane protection by Ca2+ and Zn2+.
This review focusses on two questions: (1) How can the intracellular toxicity of ions such as Ca2+ or Zn2+ be reconciled with their extracellular benefit? (2) Why is the dietary requirement for Zn2+ so high when its documented biological role is that of a tightly-bound prosthetic group of certain enzymes? An answer to both questions is provided by the observation that extracellular cations such as Ca2+ and Zn2+ protect the plasma membrane of cells against non-specific leakage, including an influx of Ca2+ or Zn2+. It is suggested that such protection, against leakage induced by microbial and other toxins, may contribute to the high dietary requirement for zinc. These arguments lead to the proposal that a previously unrecognized form of host defence is one of protection of the cell plasma membrane by divalent cations against damage induced by cytotoxic agents of environmental origin.
Pasternak
C A
CA
Department of Biochemistry, St George's Hospital Medical School, London.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002413:Cations, Divalent; D002462:Cell Membrane / Q000502:physiology*; D002463:Cell Membrane Permeability; D003593:Cytoplasm / Q000502:physiology; D004032:Diet; D006801:Humans; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology; D015032:Zinc / Q000502:physiology*
D002413:Cations, Divalent; D000254:Sodium-Potassium-Exchanging ATPase; D015032:Zinc; D002118:Calcium