Allopurinol
Effect of uric acid on plasma levels of 1,25(OH)2D in renal failure.

Vanholder R, Patel S, Hsu CH.

Department of Medicine, University Hospital, Ghent, Belgium.

Previous studies from these laboratories have demonstrated that uremic biologic fluids contain substances that suppress 1,25(OH)2D metabolism. Among these substances, it was found that uric acid suppresses 1 alpha-hydroxylase activity and synthesis of 1,25(OH)2D in rats. In this study, the effect of uric acid on plasma concentrations of 1,25(OH)2D in patients with renal failure was examined. Nine patients with stable chronic renal failure (serum creatinine, 1.9 to 6.4 mg/dL) were studied. None of the patients received vitamin D supplementation. Plasma concentrations of Ca, P, parathyroid hormone, creatinine, uric acid, 1,25(OH)2D, and 25(OH)D were measured before and 1 wk after the patients received allopurinol, 300 mg daily. Plasma creatinine, Ca, P, parathyroid hormone, and 25(OH)D did not change before or after allopurinol treatment. However, plasma uric acid decreased significantly from 7.3 +/- 0.4 to 4.0 +/- 0.4 mg/dL (P < 0.01) and plasma concentration of 1,25(OH)2D rose from 30.8 +/- 2.7 to 38.2 +/- 4.8 pg/mL (P < 0.01) after the ingestion of allopurinol. Allopurinol itself did not appear to directly enhance 1 alpha-hydroxylase activity in rats. It was concluded that a short-term administration of allopurinol suppresses plasmic uric acid and increases plasma 1,25(OH)2D in patients with chronic mild to moderate renal failure.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8286711&dopt=Abstract allopurinol Zyloprim



Allopurinol
Allopurinol protects the bowel from necrosis caused by indomethacin and temporary intestinal ischemia in mice.

Krasna IH, Lee RT.

Department of Surgery, UMDNJ-Robert Wood Johnson Medical School, New Brunswick 08903-0019.

The present study was undertaken to evaluate if allopurinol administration protects mice from bowel necrosis caused by temporary intestinal ischemia followed by indomethacin (INDO). We have previously reported that ischemia (15-minute occlusion of superior mesenteric vessels) followed by intravenous (i.v.) INDO caused significant bowel necrosis in CD-1 mice. Ischemia or INDO alone did not cause necrosis. To investigate protective measures against necrosis, we used CD-1 mice, 25 to 30 g. Forty-four animals were gavage fed 1 mL of water for 7 days and 32 animals were gavage fed 10 mg/kg allopurinol for 7 days. On the seventh day all animals were anesthetized and the superior mesenteric vessels occluded for 15 to 20 minutes, followed by i.v. INDO (0.5 mg/kg) once daily for 3 days. Animals who died were examined for bowel necrosis and all animals were killed 7 days after surgery and necropsied. Of the 44 saline-fed animals, 12 developed bowel necrosis (27%). Of the 32 allopurinol-fed animals, 1 developed necrosis (3%). The result of Fisher's exact two-tailed test was P = .006. Pretreatment with oral allopurinol significantly protects the mice from developing bowel necrosis when the mesenteric vessels are temporarily occluded and INDO is administered. Allopurinol may prevent reperfusion injury by inhibiting formation of xanthine oxidase generated, oxygen-derived free radicals and may be valuable in pretreating premature infants with patent ductus arteriosus who have had an ischemic episode in whom INDO use is contemplated.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8308686&dopt=Abstract allopurinol Zyloprim



Allopurinol
Correlation of red cell antioxidant status and heart-lung function in swine pretreated with allopurinol (a model of heart-lung transplantation).

Qayumi AK, Godin DV, Jamieson WR, Ko KM, Poostizadeh A.

University of British Columbia, Vancouver, Canada.

Although the protection against myocardial ischemia-reperfusion injury by allopurinol has previously been attributed to inhibition of xanthine oxidase, the demonstration of protective effects in species devoid of detectable myocardial xanthine oxidase activity argues against this hypothesis. In the present study, the effects of allopurinol pretreatment in a model of heart-lung transplantation were examined in swine, a species devoid of myocardial xanthine oxidase activity. Twenty-eight experiments were performed utilizing the heart-lung transplantation model--seven controls (14 animals, 7 donors and 7 recipients) with no preoperative pharmacological intervention, and twenty-one in the experimental group (42 animals, 21 donors and 21 recipients) with donor and recipient pretreated with allopurinol 50 mg/kg/day for 3 days. The effect of allopurinol was determined on day 2 blood samples assessing red cell antioxidant status by measurement of malondialdehyde (MDA) formation in response to in vitro peroxidative challenge. The experimental group was divided into subgroups--namely, nonresponders (8 pairs of animals) and responders (13 pairs of animals) based on the range (mean +/- 2 SD) of erythrocyte MDA levels in the control group. Heart-lung transplantation was performed in the three groups (control [7], nonresponders [8], and responders [13]) on day 3 following the final dose of allopurinol administration in the experimental group. Based on postsurgical assessments of cardiac and pulmonary function integrity, animals showing the greatest red cell antioxidant response following allopurinol treatment showed significantly better recovery compared with the control group. In contrast, animals that did not respond to allopurinol pretreatment showed results similar to those of the control (i.e., untreated) group. Furthermore, red cell MDA levels in all the allopurinol-treated animals were found to correlate positively (P < 0.001) with the extent of myocardial and lung dysfunction, as indicated by cardiac index and lung water measurements, respectively. The present study suggests that allopurinol protection against ischemia-reperfusion injury may involve generalized alterations in tissue antioxidant status, and that the measurement of erythrocyte susceptibility to oxidative challenge could provide a useful approach to optimizing the effectiveness of therapeutic interventions undertaken prior to surgery in order to minimize the risk of damage resulting from postischemic tissue reperfusion.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8333065&dopt=Abstract allopurinol Zyloprim



Allopurinol
Interaction between allopurinol and copper: possible role in myocardial protection.

Malkiel S, Har-el R, Schwalb H, Uretzky G, Borman JB, Chevion M.

Department of Cellular Biochemistry, Hebrew University-Hadassah School of Medicine, Jerusalem, Israel.

Allopurinol, a potent inhibitor of xanthine oxidase, is known to effectively protect the heart against damage in patients undergoing cardiac bypass surgery. There is still an ambiguity concerning the presence of xanthine oxidase in the human heart. Thus, the mechanism underlying the protective effect of allopurinol is unclear. Transition metal ions, such as iron and copper, can participate in single-electron reactions and mediate the formation of oxygen-derived free radicals. In this study the interaction between allopurinol and Cu(II) was investigated. Spectrophotometric investigation shows that allopurinol (0-0.8 mM) form a 1:1 complex with Cu(II) ions (0-0.8 mM) with a specific absorbance peak at 364 nm. Also, the rate constant (k) for the copper-catalyzed aerobic oxidation of ascorbate was markedly decreased in the presence of allopurinol (from 0.068 min-1 to 0.014 min-1). Allopurinol substantially reduced the copper-mediated and ascorbate-driven DNA breakage. Spectrophotometric measurements did not indicate a specific interaction between iron ions and allopurinol. It is suggested that the beneficial effects of allopurinol during reperfusion of the heart could stem from its chelation of copper, yielding a complex with low redox activity.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8349148&dopt=Abstract allopurinol Zyloprim



Allopurinol
Adsorption of allopurinol and ketotifen by chitosan.

Alkhamis KA, Obeidat WM, Najib NM.

Jordan University of Science and Technology, Irbid, 22110, Jordan. khou just.edu.jo

The experimental work of studying the adsorption of ketotifen and allopurinol by chitosan focused on determining the solubilities and the adsorption isotherms of the adsorbates employed in this study. The adsorption of the aforementioned compounds by chitosan was studied using the rotating bottle method. The concentrations, both before and after the attainment of equilibrium, were determined with the aid of a reversed-phase high-performance liquid chromatography column. The results of these studies demonstrated that ketotifen and allopurinol are both adsorbed by chitosan. The nonlinear Langmuir-like and the Freundlich models both were applied to the experimental data. The correlation coefficients obtained from the nonlinear Langmuir-like model were better than those obtained from Freundlich model, suggesting that allopurinol and ketotifen interacted with certain specific binding sites on the chitosan surface. The allopurinol adsorption experiments indicated that the particle size of chitosan and therefore the surface area can significantly affect the Langmuir capacity constant, while the affinity constants are statistically the same. As expected from the solubility studies, the ketotifen adsorption experiments at 2 different pHs (7 and 10) showed that the adsorption affinity at pH 10 was much higher than at pH 7. What was not expected was that the capacity constants were significantly different, suggesting that further studies are needed using common ion buffers and multicomponent adsorption for the proper mechanism to be determined.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14727888&dopt=Abstract allopurinol Zyloprim



Allopurinol
Allopurinol inhibition of neutrophilic alveolar response during hyperoxia.

Bryan CL, Lewis RE, Owens SL, Emanuel B, Jenkinson SG.

Department of Medicine, University of Texas Health Science Center, San Antonio.

Allopurinol is a potent xanthine oxidase inhibitor that has been administered to animals to protect tissues from oxidant injury. We hypothesized that allopurinol may protect against oxidant injury by inhibiting the inflammatory response. Male Sprague-Dawley rats were injected daily with vehicle or allopurinol and compared with noninjected controls. Animals were exposed to room air or 90% oxygen for 14 days. At the end of the exposure period, all animals were lavaged and bronchoalveolar lavage fluid (BALF) was examined for cell counts, lactate dehydrogenase (LDH), and protein. BALF neutrophils were significantly increased in oxygen-exposed noninjected controls (33 +/- 7 x 10(3)/mm3) and also in the vehicle-inoculated oxygen-exposed animals (43 +/- 6 x 10(3)/mm3). Allopurinol treatment resulted in a decrease in the neutrophilic alveolar response in oxygen-exposed animals (5.3 +/- 4 x 10(3)/mm3, P < 0.001). These data reveal that oxygen exposure produces a neutrophilic alveolar response that is attenuated by allopurinol treatment. BALF protein and LDH were significantly increased in all inoculated and noninoculated oxygen-exposed animals compared with air-exposed animals. Therefore, allopurinol decreases the neutrophilic alveolar response produced by a hyperoxic exposure in the rat but does not decrease lung injury as assessed by alveolar LDH and protein release.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8376286&dopt=Abstract allopurinol Zyloprim