Abnormal purine and pyrimidine nucleotide content in primary astroglia cultures from hypoxanthine-guanine phosphoribosyltransferase-deficient transgenic mice

Lesch-Nyhan syndrome is a pediatric metabolic-neurological syndrome caused by the X-linked deficiency of the purine salvage enzyme hypoxanthine-guanin e phosphoribosyltransferase (HGPRT), The cause of the metabolic consequence s of HGPRT deficiency has been clarified, but the connection between the en zyme deficiency and the neurological manifestations is still unknown. In se arch for this connection, in the present study, we characterized purine nuc leotide metabolism in primary astroglia cultures from HGPRT-deficient trans genic mice. The HGPRT-deficient astroglia exhibited the basic abnormalities in purine metabolism reported before in neurons and various other HGPRT-de ficient cells. The following abnormalities were found: absence of detectabl e uptake of guanine and of hypoxanthine into intact cell nucleotides; 27.8% increase in the availability of 5-phosphoribosyl-1-pyrophosphate; 9.4-fold acceleration of the rate of de novo nucleotide synthesis; manyfold increas e in the excretion into the culture media of hypoxanthine (but normal excre tion of xanthine); enhanced loss of label from prelabeled adenine nucleotid es (loss of 71% in 24 h, in comparison with 52.7% in the normal cells), due to 4.2-fold greater excretion into the media of labeled hypoxanthine. In a ddition, the HGPRT-deficient astroglia were shown to contain lower cellular levels of ADP, ATP, and GTP, indicating that the accelerated de novo purin e synthesis does not compensate adequately for the deficiency of salvage nu cleotide synthesis, and higher level of UTP, probably due to enhanced de no vo synthesis of pyrimidine nucleotides. Altered nucleotide content in the b rain may have a role in the pathogenesis of the neurological deficit in Les ch-Nyhan syndrome.