Sorption of Heavy Metal Cations by Corn Mitochondria and the Effects on Electron and Energy Transfer Reactions

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Abstract
The passive sorption of Pb+2, Cd+2, Zn+2, Co+2, Ni+2, and Mn+2 by isolated corn mitochondria was determined, and, except for Pb+2, the maximum sorption for each cation was about 58 nmol per milligram of protein. Sorption of Pb+2 was apparently ten times greater, but precipitation may have been the cause of this larger value. The effects of Pb+2, Cd+2, Zn+2, Co+2, and Ni+2 on acceptorless rates of electron transport for three substrates were determined. Greater than 50% inhibitions of oxidation were observed for succinate after additions of >0.1 mM Cd+2, Zn+2, or Pb+2: for NADH after additions of >0.5 mM Cd+2 or Zn+2; and for malate + pyruvate after additions of >0.1 mM Cd+2. Some inhibition of the rate of substrate oxidation was observed for most cations at higher concentrations. Coupling, as measured by ADP/O ratios, was inhibited at lowest concentrations by Cd+2 or Zn+2 and at higher concentrations by Co+2 or Ni+2. Substantial swelling of mitochondria oxidizing succinate was observed following additions of O.1 mM Cd+2 or Pb+2, Correlations are drawn between the effects of Pb+2, Cd+2, Zn+2, Co+2, and Ni+2 and their sorption to mitochondrial membranes.

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