[The effect of posthypoxic hypothermia for lactate dehydrogenase activity in brain cortex and blood serum of 14-days-old rats].
OBJECTIVE
The effect of various degrees of hypobaric hypoxia and consequent hypothermia on lactate dehydrogenase (E.C.1.1.1.27) activity in blood serum and brain cortex in 14 day-old rats was investigated.


METHODS
Experimental study.


METHODS
Institute of Physiology, 1st Med. Faculty, Charles University, Prague.


METHODS
14 day-old rats (Wistar of our own breed) were exposed to mild hypobaric hypoxia (corresponding to altitude of 7000 m, pO2 = 8.6 kPa, BP = 41.2 kPa, lasting 20 min) or strong hypobaric hypoxia (corresponding to altitude of 9000 m, pO2 = 6.4 kPa, BP = 30.7 kPa, lasting 30 min). Just after hypoxic stress the animals were killed by decapitation and on cooled block the grey cortical matter was removed. Blood serum samples as well as brain cortex homogenates were immediately incubated in three variously tempered media (38 degrees Celsius = control values, 30 degrees Celsius and 22 degrees Celsius = hypothermic conditions). The incubation was over (30 min.), and the lactate dehydrogenase (LDH) activity was followed using the Lachema test.


RESULTS
The LDH activity was influenced by mild hypobaric hypoxia (7000 m) neither in blood serum nor in brain cortex. Also the values of LDH activities registered in normo or in hypothermic conditions were not different as compared with control values. The strong hypoxia (9000 m) evokes in brain cortex homogenates simultaneously with normothermia and posthypoxic hypothermia (30 degrees Celsius) significant increase of LDH activity. In blood serum the strong hypoxia increased the LDH activity; in subsequent hypothermic condition (22 degrees Celsius) the LDH activity was more lowered.


CONCLUSIONS
The LDH activity in brain cortex as well as in blood serum of young rats (Wistar) seems to be resistent to mild hypoxia (7000 m) as well to hypothermic conditions. The strong hypoxia (9000 m) evokes quite different responses: in brain cortex the LDH activities in hypothermic conditions are higher, in blood serum lower as compared with control values (14 day-old rats stressed by hypoxia only). In control measurements the lowering temperature decreases the mentioned enzyme activity in brain cortex; in blood serum no significant differences could be found.
Smídová
L
L
Fyziologický ústav 1. LF UK, Praha.
Mourek
J
J
Slapetová
V
V
Dohnalová
A
A
D000399:Air Pressure; D000818:Animals; D000831:Animals, Newborn; D002540:Cerebral Cortex / Q000201:enzymology*; D003080:Cold Temperature; D002534:Hypoxia, Brain / Q000201:enzymology*; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000097:blood / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D007770:L-Lactate Dehydrogenase
Vliv a význam hypoxie a následné hypotermie na aktivitu laktátdehydrogenázy v mozkové kůre a v krevním séru u 14denních laboratorních potkanů.