The activity and localization of enzymes in blood leukocytes were examined in dark brown (+/+), silver-blue (p/p) and sapphire (a/a p/p) minks during several periods of postnatal development. This study was performed by morphometric and cytochemical methods using light microscopy and image analysis software “VidеoTest». Significant genotypic differences were determined in the distribution of peroxidase, naphthol AS-D chloroacetate esterase (NASDCE) and alkaline phosphatase (AP) in leukocytes. Sapphire mink (a/a) are characterized by the lowest reproductive potential and increased postnatal mortality among the studied genotypes. Leukocytes of sapphire mink showed a significant increase in the size of and a change in the number of peroxidase- and esterase-positive structures, as well as the presence of phosphatase-negative areas in the cytoplasm. Apparently, these structures are abnormal granules and indicate the disturbance of granulogenesis. Mink of all the three genotypes demonstrated similar age-related changes of peroxidase and alkaline phosphatase activities. The lowest peroxidase activity was observed in early postnatal development, whereas the highest – at the age of 120 days. The increase in alkaline phosphatase activity occurred during the phase of active growth – on the 60th day of postnatal ontogeny. The pattern of age-related changes in NASDCE activity depended on the mink’s genotype. Sapphire mink had the highest level of NASDCE activity at the age of 4 days and the lowest – at 180 days, whereas both dark brown and silver-blue mink at the same age (180 days) had the highest values of NASDCE activity.
The postnatal dynamics of the enzymes’ activity in the three genotypes apparently reflects the specific features of metabolism in leukocytes in different periods. The cytochemical features of peripheral blood leukocytes in sapphire mink suggest the presence of a morphofunctional cellular defect, which is the cause of the animals’ low viability.