Summary
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1.
In vivo uricase activity was tested in rats by injection of 2-C14 urate and measurement of the total C14 activity and the fractional activities of allantoin, allantoic acid and urea in samples of blood and urine. In control animals, 5 min after the injection, 70% of the plasma tracer was already present in the form of allantoin. No allantoic acid and urea were produced. Intestinectomy had no measurable influence on uricase activity. On the other hand, hepatectomy or ligation of the hepatic artery combined with subtotal viscerectomy did abolish uricase activity almost completely.
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2.
Following microinjections into proximal tubules of Ringer solution containing 2-C14 urate, urine samples during early recovery mainly contained labelled urate, whereas in later samples the fraction of labelled allantoin increased. About 12 min after the microinjection the urine of both kidneys contained equal amounts of tracer mainly in the form of allantoin.
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3.
When segments of proximal tubules were perfused with an equilibrium solution containing tracer amounts of C 14 urate, no urate was metabolized during its passage through the proximal tubule.
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4.
C 14 urate was offered from the peritubular capillaries and samples of tubular fluid were analyzed, Again, all the tracer in the tubular fluid was in the form of urate, indicating that urate is not oxidized when it is transported across the tubular cell.
It is concluded from these results that: 1. The rat kidney has no significant uricase activity. 2. Urate transport in the kidney is not influenced by this enzyme. 3. The degradation of urate to allantoin takes place at extrarenal sites, mainly in the liver.
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References
Bernheim, F., Bernheim, M. L. C.: The purine metabolism of rat liver and kidney slices in vitro. Arch. Biochem.12, 249–255 (1947)
Boudry, J. F., Roch-Ramel, F.: Untersuchung der transtubulären Harnsäurebewegungen mittels kontinuierlicher Mikroperfusion bei der Ratte. In: Niere und Stoffwechsel, VII. Symp. Ges. Nephrol. Tübingen 1970, Hrsg. A. Bohle und G. E. Schubert: Stuttgart-New York: Schattauer 1971
Byers, S. O., Friedman, M., Garfield, M. M.: The blood uric acid and allantoin of the rat after nephrectomy and hepatectomy. Amer. J. Physiol.150, 677–681 (1947)
Christen, Ph., Peacock, W. C., Christen, A. E., Wacker, W. E. C.: Urate oxidase in primate phylogenesis. Europ. J. Biochem.12, 3–5 (1970)
Florkin, M., Duchâteau, G.: Les formes du système enzymatique de l'uricolyse et l'évolution du catabolisme purique chez les animeaux. Arch. int. Physiol.53, 267 (1943)
Greenberg, D. M.: Metabolic pathways, Vol. IV, pp. 37–39. New York-London: Academic Press 1970
Kramp, R. A., Lassiter, W. E., Gottschalk, C. W.: Urate 2-14C transport in the rat nephron. J. clin. Invest.50, 35 (1971)
Lang, F., Greger, R., Deetjen, P.: Handling of uric acid by the rat kidney. II. Microperfusion studies on bidirectional transport of uric acid in the proximal tubule. Pflügers Arch.335, 257–265 (1972)
Oelert, H., Baumann, R., Gekle, D.: Permeabilitätsmessungen einiger schwacher organischer Säuren aus dem distalen Konvolut der Rattenniere. Pflügers Arch.307, 178–189 (1969).
Sonnenberg, H., Deetjen, P.: Methode zur Durchströmung einezelner Nephronabschnitte. Pflügers Arch. ges. Physiol.278, 669 (1964)
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Partially supported by “Österreichischer Fonds zur Förderung der wissenschaftlichen Forschung”.
Receiving scholarships from “Deutsche Forschungsgemeinschaft”.