Modified fluorescent spot test for glutathione peroxidase and selenium concentration in sheep blood.

A modified fluorescent spot-test procedure for the determination of glutathione peroxidase activity in whole blood is described. After correcting for differences in the packed cell volumes of blood samples the times required for the defluorescence of reduced nicotinamide dinucleutide phosphate in spot tests were correlated in a logarithmic manner with glutathione peroxidase activities measured spectrophotometrically. Since the glutathione peroxidase activity and selenium concentration in whole blood samples of sheep are linearly related an equation was generated for the estimate of the selenium concentration in the blood of sheep using spot-test indices. The sensitivity and repeatability of the spot-test procedure allows it to be used for the routine screening of large numbers of blood samples.