Über die d-Aminosäure-Oxydase in Leberextrakten von Ratten mit chemisch induzierten Tumoren

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Abstract
Fresh Walker tumor tissue is ground with sand, extracted with M/5 phosphate buffer (pH 8), and the mixture is centrifugalized. Ten ml. of extract are obtained from 20 g. tumor tissue. This extract is mixed with liver extract of normal rats in the ratio 2:5. For a control, the same normal liver extract is diluted with a corresponding amt. of the phosphate buffer. The O2 consumption of the liver extracts is detd. in the Warburg apparatus at 37.5[degree]. The reaction mixtures usually contain 2.1 ml. tissue extract, 44.5 mg. dl-alanine in 1 ml. M/2 phosphate buffer, (pH 8), and 0.1 ml. 2 N KOH. The expts. show that the d-amino acid oxidase activity of the normal liver extract is not inhibited by the tumor extract, the O2 consumption in the presence of tumor extract being 245 cmm., and in the absence of tumor extract, 247 cmm. Rats are inoculated with a hash of the rapidly growing Jensen sarcoma. In about 3 wks. the sarcomas developed weigh 35 g. The d-amino acid oxidase activity of the liver extracts of these rats, as is true for rats with Walker tumors, is much lower than that of extracts prepared from the livers of normal control rats. Rats are injected under the skin with 10 mg. benzopyrene or methylcholanthrene in oil. After 41/2-6 months, slow-growing tumors 10-50 g. in weight develop. Extracts prepared from the livers of these rats have the same d-amino acid oxidase activity as extracts prepared from the livers of normal rats. Normal d-amino acid oxidase activity in liver extracts cannot, therefore, be taken as an indication of the absence of tumors. The decrease in d-amino acid oxidase activity of liver extracts is due to a lack of apo-enzyme. One vol. of liver tissue is ground in a mortar with 10 vols. of 0.25 M phosphate buffer, pH 7, and the total protein and albumin in the extract detd. gravimetrically. In rats with Walker tumors, it is not possible to correlate a decrease in the d-amino acid oxidase of the liver with changes in the liver proteins.

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