We studied age-related changes in the activity of calpain, those in the activity of its endogenous inhibitor calpastatin, and the ratio of these indices in the brain of rats of four age groups (2-3 weeks, 2-3, 5-6, and 24 months). The activity of calpain was estimated using FITC casein as the substrate. In a soluble fraction of the brain homogenate, the enzyme activity in general increased with age. In mature rats (5 to 6 months old), this index exceeded 3.65 times the corresponding index in juvenile (2 to 3 weeks old) animals, while in old animals this index somewhat decreased. In the fraction obtained after separation of calpain from other components using DEAE-cellulose chromatography, the age-related trend toward an increase in the activity of calpain was preserved, but it was much more moderate. The activity of calpastatin demonstrated an opposite direction of age changes: it was the maximum in 2-3-week-old animals and gradually decreased (by 27%) in old rats. We also found that the efficacy of inhibitory action of calpastatin in the cerebral tissue with respect to the activity of calpain was, as a rule, redundant. In this case, the ratio of inhibitor/enzyme activities decreased with age; this index was 1.65, 1.33, 1.1, and 1.0 or less in 2-3-week-old, 2-month-old, mature, and old animals. Therefore, we found that the intensity of calpain-mediated proteolysis in the rat brain increases from the juvenile period to the mature age and somewhat decreases in old individuals. Such alterations are developed at the expense of both an increase in the activity of the enzyme and weakening of the action of its inhibitor (calpastatin).
We investigated the actions of human recombinant a2-interferon and a secondary messenger of its action, 2'-5'-oligoadenylate, on tetrodotoxin (TTX)-sensitive sodium transport using human (IMR-32) and murine (NIE-115) neuroblastoma ceils. In biochemical experiments using 22Na, human interferon was shown to increase entry of 22Na into IMR-32 neuroblnstoma cells through the channels activated by veratrine and scorpion toxin. This increase was clearly dose-dependent. Cell treatment with "ITX completely inhibited this sodium transport. On the contrary, 2'-5'-oligoadenylate depressed entry of ZZNa into neuroblnstoma cells. The activation effect was not observed under the action of human a2-interferon on TTX-sensitive sodium flows to the routine neuroblastoma cells, which demonstrated the species-related specificity of this agent.
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