Nickel fixation by rat plasma and 21-day placental homogenates

The effectiveness of 19-day placenta homogenates in the binding and retention of nickel was compared with that of rat plasma in a simple dialysis system. The energy of activation of both placenta and plasma were of the same range (-5 kJ/mol). The specificity of the nickel binding system was considerable, as the presence of concentrations of zinc, iron or copper five orders of magnitude larger resulted only in the loss of a maximum of 10% of the pre-bound nickel in 24 h at 20 degrees C. This strong fixation of nickel seems to be specific and is probably the same in placenta and in plasma.