Determination of glutathione peroxidase activity in human milk.

An analytical method for determining glutathione peroxidase (GPx) (EC 1.11.1.9) activity in whole blood has been adapted to human milk samples. The values obtained for precision (relative standard deviation: 8.4%), linearity and accuracy (recovery: 90.4%) indicate the adequacy of the method for the mentioned purpose. The method was applied to 11 human milk samples obtained in the range from 6 to 135 days post partum. The resulting GPx activities (83.3 +/- 23.6 U/L) did not correlate to the selenium content of the samples, though a reciprocal correlation was found between the duration of lactation and milk GPx activity.