The uptake of nucleobases was investigated across the basolateral membrane of the sheep choroid plexus perfused in situ. The maximal uptake (U(max)) for hypoxanthine and adenine, was 35.51+/-1.50% and 30.71+/-0.49% and for guanine, thymine and uracil was 12.00+/-0.53%, 13.07+/-0.48% and 12.30+/-0.55%, respectively with a negligible backflux, except for that of thymine (35.11+/-5.37% of the U(ma...

We have observed that the elevated plasma adenosine levels are associated with hyperuricemia in nonpreeclamptic twin pregnancies. In animal models, extracellular adenosine is taken up by cells to form adenine nucleotides or is degraded to other purine metabolites such as hypoxanthine, which is further metabolized to xanthine and uric acid. In this study, we measured plasma hypoxanthine levels t...

We postulated that adenosine function could be related to some of the neurological features of Lesch-Nyhan syndrome and therefore characterized adenosine transport in PBLs (peripheral blood lymphocytes) obtained from Lesch-Nyhan patients (PBL(LN)) and from controls (PBL(C)). Adenosine transport was significantly lower in PBL(LN) when compared with that in PBL(C) and a significantly lower number...

A B S T R A C T A case of xanthinuria is briefly described, and the results of in vivo studies with 4C-labeled oxypurines are discussed. The data demonstrate that the rate of the turnover of uric acid is normal, despite an extremely small uric acid pool. Xanthine and hypoxanthine pools were measured and their metabolism evaluated. The bulk of the daily pool of 276 mg of xanthine, but only 6% of...

Certain gouty subjects with excessive de novo purine synthesis are deficient in hypoxanthineguanine phosphoribosyltransferase (HG-PRTase [EC 2.4.2.8]). The mechanism of accelerated uric acid formation in these patients was explored by measuring the incorporation of glycine-(14)C into various urinary purine bases of normal and enzyme-deficient subjects during treatment with the xanthine oxidase ...

It was previously reported (1) that dietary adenine is utilized by the rat as a precursor of both the adenine and the guanine of nucleic acids. Although several compounds containing 1 to 3 carbons have been shown to be incorporated into uric acid (2, 3) or guanine (4), none of the more complex precursors of the purine ring has been identified. The postulation that the immediate metabolic precur...

The Effect of orally given allopurinol in the distribution of intravenously administered 14C-hypoxanthine radioactivity was studied in squirrel monkeys 8 hr after administration of the label by the whole body autoradiography. Although the distribution of radioactivity in the normal and allopurinol-treated animals was essentially similar to each other, more intense radioactivity was noted in the...

The structural requirements for the binding of purines to adenine phosphoribosyltransferase from monkey liver were explored by the determination of the K; values for 67 purines and purine analogues. Adenine was bound 40 times better than the most effectively bound analogues. Substitutions on the 6-amino group of adenine decreased binding to varying degrees. The hydroxylaminoand hydrazinopurines...

The overall metabolism of purines was studied in tobacco (Nicotiana tabacum) mesophyll protoplasts. Metabolic pathways were studied by measuring the conversion of radioactive adenine, adenosine, hypoxanthine and guanine into purine ribonucleotides, ribonucleosides, bases and nucleic acid constituents. Adenine was extensively deaminated to hypoxanthine, whereupon it was also converted into AMP a...