[Lactate dehydrogenase in the rainbow trout (S. irideus Gib.)]

Experiments were carried out to study the activity of the serum lactatedehydrogenesis in 1167 rainbow trout (S. iredeus Gib.), raised in Karst and in river water, in order to establish the normal and the plasma enzyme levels depending on age, sex and season. It was proved that with the fish raised in Karst water the average plasma enzyme activity varies from 1627 to 2567 UI, the highest being with the one-year old fish and with the advance of age it diminishes to 1627 UI with the three-year old female ones. The highest enzyme activity was observed with all ages during the summer-autumn season, whereas in spring and in winter it was comparatively low. With the fish raised in river water the activity of the serum lactatedehydrogenesis vacillated within the boundaries between 2340 and 3350 UI. It was highest with the two-year old male ones--3400 UI, and lowest with the one-year old ones--2340 UI. The season alterations in the activity of enzyme were analogical with all age-groups--it decreased from spring till summer, reached its maximum in autumn, and then it decreased abruptly and reached its minimum in winter.