Effects of Hypothermia and Self-Warming on Activity of Ca(2+)-Dependent Neutral Proteases in Tissues of Ground Squirrels and Rats.

Effects of hypothermia and subsequent self-warming on activity of Ca(2+)-dependent neutral proteases were studied in tissues of ground squirrels and rats. Moderate hypothermia did not significantly change activity of Ca(2+)-dependent neutral proteases in the analyzed tissues of ground squirrels, but reduced protease activity in rat heart. Severe hypothermia reduced enzyme activity in the analyzed tissues of rats and ground squirrels. Differences in activity of Ca(2+)-dependent neutral proteases after long-term hypothermia and subsequent self-warming were found only in the heart.

Activity of Ca2+-dependent neutral proteases in tissues of ground squirrel during hibernation and during self-warming after induced awakening.

Cyclic changes in activity of Ca2+-dependent neutral protease occur during preparation for hibernation, with an increase in September and November and decrease in October and December. During hibernation proteolytic enzyme activity decreased, while during self-warming after induced awakening, the role of Ca2+-dependent processes in the tissues of ground squirrels increased according to the body temperature.

Changes in activity of neutral proteases in tissues of ground squirrels in the dynamics of hibernation.

Total activities of neutral proteases in the cerebral, hepatic, and myocardial tissues of ground squirrel vary during hibernation: in autumn (before hibernation) activities of the enzymes in the brain and myocardium start increasing, while in the liver they do not change. A common feature for all tissues is minimum activity of active neutral proteases in the middle of hibernation month 1 bout, while the maximum activity is recorded before awakening.

[Peptide hydrolase activity in brain tissues during the early stages of post-hypothermia period]. / Peptidgidrolaznaia aktivnost' v tkaniakh mozga na rannikh étapakh postgipotermicheskogo perioda.

The acid peptidohydrolase activity in the homogenate, dissoluble and mitochondrial-lysosomal fractions of brain tissues of rats who have endured deep hypothermia was determined after their "active" warming for an hour and on the 1st, 2nd, 3d and 7th days after their self-warming. The "active" warming of rats who have endured deep hypothermia (19-20 degrees C) brings about the restoration of the acid peptidohydrolase activity in the subcellular brain tissue fractions. After self-warming the examined enzyme activity restores 7 days later. In the dynamics of the posthypothermic period a change in the acid peptide hydrolase distribution in fractions occurs on the 2nd-3d days.

[Effect of hypothermia on subcellular distribution and various physico-chemical properties of cathepsin D in rat brain]. / Vliianie gipotermii na subkletochnoe raspredelenie i nekotorye fiziko-khimicheskie svoistva katepsina D v golovnom mozgu krys.

The total cooling ef rats down to the rectal temperature 30 degrees and 20 degrees C does not change significantly the ratio of the relative specific activity of cathepsin D in subcellular fractions of the rat brain. The gel chromatographic analysis of heterogeneity of cathepsin D molecular forms in subcellular fractions established the presence of a high-molecular (in the fractions of lysosome and microsome mitochondria) and a low-molecular (in the fractions of lysosome and cytosol mitochondria) enzyme forms. Under hypothermia (20 degrees C) in the brain cytosol fraction there arises a minor zone of the cathepsin D activity corresponding to the high-molecular enzyme form.

[Activity and temperature dependence of acid peptidohydrolase in cerebral tissue of adrenalectomized rats under moderate hypothermia]. / Aktivnost' i temperaturnaia zavisimost' kisloi peptidgidrolazy v tkani mozga adrenaléktomirovannykh krys pri umerennoi gipotermii.

The activity of acid peptidohydrolase and its temperature dependence were determined in the cerebral cortex and totally in the midbrain and diencephalon of rats in normal state after a false operation and with bilateral adrenalectomy as well as under moderate (30 degrees C) hypothermia of intact, false-operated and adrenalectomized animals. The enzyme activity is established to change more significantly in the cerebral cortex. Adrenalectomy lowers it in the cortex at an incubation temperature of 30 and 20 degrees C. Incubation at a temperature of 37, 25, 20 and 15 degrees C decreases this activity under animal cooling as well. A combined effect of hypothermia and adrenalectomy on the enzyme activity is not additive.

[Brain peptide-hydrolase activity in hypothermia]. / Peptid-gidrolaznaia aktivnost' taknei mozga pri gipotermii.

The cooling of rats to the body temperature of 30 and 25 degrees C does not change acidic peptide-hydrolase activity in tissue homogenates of cerebral cortex, hypothalamus, thalamus, hippocampus, midbrain, cerebellum and medulla oblongata. In deep hypothermia (to 20 degrees C) there occurs a significant increase in the peptide-hydrolase activity in tissue of the studied brain areas both in an incubation sample at 37 degrees C, and at temperature corresponding to the body temperature of cooled animals (20 degrees C). But the enzyme activity remains unchanged in homogenates of medulla oblongata incubation at 37 degrees C.