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A high-performance liquid chromatographic method was developed for the determination of plasma purine nucleoside phosphorylase activity. In this method, the reaction mixture consisted of 15 microliters of plasma and 285 microliters of 50 mM phosphate buffer (pH 7.4) containing 3.8 mM inosine and 0.15 mM 2-(3-cyano-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid (strong xanthine oxidase inhibitor). After the reaction, the hypoxanthine produced was monitored to express plasma purine nucleoside phosphorylase activity. By this method, the activity of purine nucleoside phosphorylase was easily determined even with a small-volume plasma sample and despite its low activity in plasma. In addition, plasma purine nucleoside phosphorylase activity can be accurately determined even if the plasma is turbid. As a result, we were able to measure plasma purine nucleoside phosphorylase activity in patients with gout or asthma and healthy subjects, whereby it was demonstrated that plasma purine nucleoside phosphorylase activity was higher in patients with asthma than in either healthy subjects or patients with gout.

This study was designed to compare the clinical outcome of prolonged immunotherapy for perennial allergic rhinitis with that of pharmacological treatment. Patients with perennial allergic rhinitis due to Dermatophagoides farinae (D. farinae) were divided into two groups; a pharmacotherapy group and an immunotherapy group. The pharmacotherapy group was treated with conventional pharmacological treatment using antihistamine tablets and topical steroid sprays and the immunotherapy group was treated with D. farinae extracts for 5 successive years. None of symptom scores at enrollment differed significantly between the groups. At 6 months and 1 year after the start of treatment the rate of decrease in each score was significantly greater in the pharmacotherapy group than in the immunotherapy group. The rate of decrease in sneezing scores, but not in the other scores, at 2 years after the start of treatment was also greater in the pharmacotherapy group than in the immunotherapy group. However, at 3 years the rate of decrease in any of the scores did not differ significantly between groups. The differences between the groups became clear-cut again after 5 years of treatment, when the rate of decrease in all of the scores was significantly greater in the immunotherapy group than in the pharmacotherapy group. Therefore, short-term treatment with pharmacological agents is probably superior to immunotherapy but, in the long-term, immunotherapy is apparently superior to pharmacological treatment with respect to clinical efficacy. In addition, prolonged immunotherapy provided long-term clinical efficacy and might provide a long-standing cure even after discontinuation of the therapy. In a questionnaire interview, approximately half of patients were very satisfied with prolonged immunotherapy and three-quarters were fairly satisfied or more. Additionally, the magnitude of improvement in nasal stuffiness contributed significantly and exclusively to the patient evaluation of immunotherapy. We propose that prolonged immunotherapy is never inferior to anti-allergenic pharmacological treatment and that it is possible to achieve long-term clinical efficacy or long-standing cure even after the discontinuation of immunotherapy, and that patients with perennial allergic rhinitis will be very satisfied with this prolonged therapeutic technique if nasal stuffiness is considerably alleviated.

Allopurinol or pyrazinamide was administered to rats treated with BOF-4272 (a potent xanthine oxidase inhibitor) to investigate to what degree xanthine dehydrogenase participates in the oxidation of these agents. BOF-4272 markedly decreased the plasma concentration and the urinary excretion of both oxypurinol and 5-hydroxypyrazinamide. It also decreased the sum of the urinary excretion of allopurinol and oxypurinol and that of pyrazinamide and its metabolites, although it did not affect the sum of the plasma concentrations of allopurinol and oxypurinol at 105 min after administration of allopurinol or the plasma concentration of pyrazinamide during the period after the administration of pyrazinamide. These results suggested that BOF-4272 almost completely inhibited the oxidation of allopurinol and pyrazinamide and had some effect on the excretion and/or the tissue incorporation of these two compounds. Since the in vitro study demonstrated that BOF-4272 did not inhibit the activity of aldehyde oxidase, which oxidized both allopurinol to oxypurinol and pyrazinamide to 5-hydroxypyrazinamide, the results suggested that xanthine dehydrogenase was the more important enzyme in converting allopurinol to oxypurinol and pyrazinamide to 5-hydroxypyrazinamide.

An ion-paired high-performance liquid chromatographic method was developed for the determination of erythrocyte aldehyde dehydrogenase activity. This method does not require pretreatment to remove hemoglobin from the hemolysate before enzyme reaction is initiated. In addition, the advantage with this high-performance liquid chromatographic method is that erythrocyte aldehyde dehydrogenase activity can be measured using whole blood without either separation or washing of erythrocytes. Therefore, it can be easily used in the determination of erythrocyte aldehyde dehydrogenase activity, which is an indication of excess alcohol consumption.

We administered xylitol intravenously to normal subjects to investigate the mechanism of xylitol-induced increase in the purine degradation in humans. Xylitol increased the plasma concentrations of hypoxanthine, xanthine and uric acid but decreased the blood concentration of pyruvic acid. The erythrocyte concentrations of IMP, AMP, ADP, glyceraldehyde 3-phosphate and fructose 1,6-diphosphate as well as the urinary excretion of hypoxanthine and xanthine were increased, while the erythrocyte concentration of ATP was decreased. In addition, the in vitro incubation studies using erythrocytes demonstrated that both xylitol-induced purine degradation and xylitol-induced inhibition of the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate were protected by pyruvic acid. These results indicate that xylitol-induced impairment of glycolysis in erythrocytes contributes to the observed xylitol-induced increase in the purine degradation in the body.