Objective: In the following study, possible protective effect of hypothermia (of various degree) on brain cortex metabolic activity in very young animals and adult rats was examined. Design: Experimental study. Setting: Institute of Physiology, 1st Med. Faculty, Charles University, Prague, Czech Republic. Methods: Homogenates of brain cortex of 14-day-old and adult rats and simultaneously blood serum were examined for lactate-dehydrogenase activity (LDH), [E.C. 1.1.1.27]. Three variously tempered incubation media (38 °C = control values, 30 °C = mild hypothermia, 22 °C = strong hypothermia) were checked. Also the adult rats (90-120 days) were examined (in the same arrangement). Results: The LDH activity in the blood serum of 14-day-old rats under hypothermic condition was unchanged as compared with control values. In their brain cortex the hypothermia evokes a signifi cant changes in LDH activity (µkat/l). In adult rats the results are different: no signifi cant changes in LDH activity in the brain cortex under hypothermic condition were found, but signi- fi cant drop in mentioned enzyme activity in the blood serum was established. Finally: in young animals the starting LDH activity in the blood serum as well as in the brain cortex was always signifi cantly higher as compared with values found in adult animals. Conclusion: The starting higher LDH activity in the blood serum as well as in the brain cortex in young rats (as compared with adults) and the different feature of LDH changes under hypothermic conditions are considered and discussed especially with the possibility of protective action of hypothermia in hypoxic and asphyxic newborns.

        Key words: hypothermia, lactatedehydrogenase, brain cortex, protection