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Sublethal doses of typhoid endotoxin distinctly increased the activities of glutamate dehydrogenase and histidine ammonium lyase in liver tissue of mice within 3 hrs and the tyrosine transaminase activity within 6 hrs after a single intraperitoneal administration. Within 24 hrs normalzation of these enzyme activities and a decrease in the urocaninase activity were observed in liver tissue. Lipid A, obtained from the endotoxin, activated glutamate dehydrogenase and histidine ammonium lyase, inhibited urocaninase but did not affect the tyrosine transaminase activity. Lipid B, isolated by a non-hydrolytic method, showed even wore distinct capacity to activate glutamate dehydrogenase and histidine ammonium lyase, but did not alter the activities of tyrosine transaminase and urocaninase in liver tissue.

In rat skin the histidase activity was observed 2--3 days before delivery; it was increased at the first days of postnatal development, achieving a maximal level at the 5th day and then it was decreased (within 2--3 weeks of postnatal development) to the level activity, which was found in adult animals. Concentration of urocaninic acid in skin correlated with the histidase activity. Content of urocaninic acid in skin and the histidase activity were altered under effect of administration of cylic-3',5'-AMP, dibutyryl cyclic-3',5'-AMP, glucagon, sodium fluoride, theophylline, actinomycin D and cycloheximide.

A procedure is described for immobilization of partially purified histidase by means of covalent binding of the enzyme with amino ethyl cellulose activated by glutaraldehyde. The preparation obtained was stable within 6 months at 5 degrees and within 40 days at 39 degrees. The preparation of immobilized histidase might be used for enzymatic synthesis of urocanic acid from histidine.

Effect of hepatotoxic agents (carbon tetrachloride and dimethyl nitrosamine) on the rate of the haptoglobin and ceruloplasmin synthesis in liver tissue was studied. In impairment of hepatocytes in the central zone of liver lobes, the distinct decrease in content of haptoglobin was shown to occur with a simultaneous increase in content of ceruloplasmin in blood serum. When parenchyma of the central zone of liver lobes regenerated, the haptoglobin content tended to normalization. The data obtained suggest that the synthesis of haptoglobin and ceruloplasmin is carried out in different zones of liver tissue lobes: haptoglobin is mainly found in the central zone and ceruloplasmin -- in the peripheral one.