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Kürzlich wurde von Welch und Coriney (1) eine qualitative Methode zum Nachweis von N-Acetyl-paminophenol (= p-Aminophenol) beschrieben, die mit zeitsparenden Modifikationen wiedergegeben ist. Der weit verbreitete Gebrauch phenacetinhaltiger Analgetika, die eine Zunahme der Ausscheidung von konjugiertem p-Aminophenol bedingen, hat zur Anwendung dieser nicht aufwendigen Methode für die Routine geführt. Seit dem Frühjahr 1965 sind bei uns mehr als 6000 Urinproben untersucht worden.

A decrease of glomerular filtration rate can be observed during accelerated catabolism of ATP in kidney. It has been proposed that this effect is due to the increase in the renal production of adenosine from ATP. The last reaction in the pathway concerned is the conversion of 5’-AMP to adenosine. We found that brush border membranes purified from homogenates of the rat renal cortex carry out this reaction. The enzyme involved in the hydrolysis has the characteristic properties of ecto-5’-nucleotidases: It is inhibited by ATP, ADP, and by α, β-methyleneadenosine-5’-diphosphate, and it is not stimulated by magnesium. All catalytic sites are accessible from the outside of the vesicles. The K_m of the enzyme for 5’-AMP is 5.77 µM. The enrichment of the 5’-AMP-hydrolyzing activity in the brush border fraction as compared to the homogenate is 9.2 ± 1.5 times. Histochemical staining of kidney sections reveals hydrolysis of 5’-AMP only at the brush border of the proximal tubule. We conclude that the brush border of the proximal tubule of the rat kidney possesses an ecto-5’-nucleotidase which has the same properties as the ecto-5’-nucleotidases in other tissues.