Aktivierung von Biopterin in der Ratte

Abstract

8a-14C-Biopterin intraperitoneally injected into rats is secreted within a short time and in a nearly quantitative amount into the urine. After feeding, 90% of the substance remains in the organism. 7-biopterin is absorbed only in small amounts and is excreted to a large extent with the feces. The absorbed labeled biopterin is equally distributed throughout the body. After three days a measureable amount of activity is found in the serum as well as in the liver and adrenals. The same level of activity occurs in regenerating liver and ascites tumour cells. After chromatographic separation of a 5% TCA soluble extract obtained from 250 g of rat livers, only 10% of the total radioactivity was found in biopterin. The remaining activity appears mainly in a weakly basic, extremely labile component. Other pterines could not be demonstrated. No biopterin is found in the TCA insoluble liver fraction. The compound occurs as a tetrahydrobiopterin in the liver in a concentration of about 75 μg; biopterin exists only in trace amounts. After fractional centrifugation of liver homogenate, approximately 90% of tetrahydrobiopterin is contained in the supernatant fraction.