A method is presented for studying the reducing activity of leukocytes of mice and rats using 2-(p-iodophenyl)-3-)p-nitrophenyl)-5-phenyltetrazolium chloride (INT).
Between 48.0 per cent and 83.8 per cent of the leukocytes of young adult mice and between 47.8 per cent and 68.0 per cent of the leukocytes of young rats showed formazan formation.
Infant mice of C3Hf and BALBf strains had appreciably fewer leukocytes with the ability to reduce tetrazolium than did young adults of their respective strains.
Healthy adult mice belonging to the leukemia susceptible AKR strain showed a relatively high degree of leukocytic reduction.
Old mice of the C3Hfstrain showed less formazan formation than young adult animals. This decrease was more marked for the male members of the species.