The effect of pH, PO2, and inorganic phosphate on the uptake and metabolism of hypoxanthine by erythrocytes has been studied. Uptake of hypoxanthine and accumulation of inosine 5'-monophosphate (IMP) were markedly increased at acid pH, high external phosphate concentrations, and low PO2. Release of accumulated IMP as hypoxanthine occurred at alkaline pH values and low external phosphate concent...

The characteristics of hypoxanthine transport were examined in purified brush-border membrane vesicles isolated from guineapig kidney. Hypoxanthine uptake in the vesicles was specifically stimulated by both Na+ and an inside-negative potential, resulting in a transient accumulation of intravesicular hypoxanthine. Na+-dependent hypoxanthine influx was saturable (apparent Km 4.4 + 2.1 ,uM, Vmax 1...

The oxidation mechanism and adsorption of inosine 5'-monophosphate and hypoxanthine were investigated in solutions of different pH using voltammetric and impedance methods at glassy carbon electrodes. For both compounds, the pH dependence from differential pulse voltammetry showed that the same number of electrons and protons are involved in the rate-determining step of the electrochemical reac...

Microvessel segments were isolated from rat brain and used for studies of hypoxanthine transport and metabolism. Compared to an homogenate of cerebral cortex, the isolated microvessels were 3.7-fold enriched in xanthine oxidase. Incubation of the isolated microvessels with labeled hypoxanthine resulted in its rapid uptake followed by the slower accumulation of hypoxanthine metabolites including...

Mammals experience some degree of hypoxia during their lifetime. In response to hypoxic challenge, mammalian cells orchestrate specific responses at transcriptional and posttranslational level which lead changes in the purine metabolites order cope with threatening conditions. The aim this study was evaluate enzymes involved metabolism human muscle Muscle culture were exposed enzymatic activity...

Fusion of the 1R mouse cell, which lacks activity of hypoxanthine phosphoribosyl transferase (EC 2.4.2.8), with chick-embryo fibroblasts yielded progeny cells that survived in hypoxanthine-aminopterin-thymidine selective medium. This property and the failure of the progeny to survive in 8-azaguanine indicated that hypoxanthine phosphoribosyl transferase activity was present. Electrophoretic ana...

The Lesch-Nyhan syndrome is characterized clinically by choreoathetosis, spasticity, selfmutilation, and mental and growth retardation. Biochemically, there is a striking reduction of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity in affected individuals. We have examined erythrocytes from 14 patients with the Lesch-Nyhan syndrome for the presence of hypoxanthine-guanine phosph...

Steady state kinetics of hypoxanthine guanine phosphoribosyltransferase-catalyzed reactions are studied. The results obtained suggest that IMP, GMP, P-Rib-PP, and pyrophosphate bind to the same enzyme form, while hypoxanthine and guanine bind to a different form. Guanine activates IMP-pyrophosphorolysis. During the reaction guanlne and IMP are consumed with formation of GMP and hypoxanthine (IM...

The involvement of protein kinase C (PKC) in the regulation of Na(+)-dependent and -independent hypoxanthine transport was investigated by exposing confluent monolayers of LLC-PK1 renal epithelia cells to the PKC activator, phorbol 12-myristate 13-acetate (PMA). Chronic exposure (> 2 h) of LLC-PK1 monolayers to 16 nM PMA resulted in approximately 75% inhibition of Na(+)-dependent hypoxanthine i...