Plasma oxypurines in gastric and colorectal cancer

Reverse phase high performance liquid chromatography has been used for the determination of plasma hypoxanthine, xanthine, and uric acid in normal subjects and in patients with gastric and colorectal cancer. Plasma oxypurines are significantly elevated in either type of cancer, while uric acid concentration is only higher in gastric cancer. The variations are related to the stage of the tumors, and the physiopathology of their occurrence is discussed.

Adenosine, inosine, and hypoxanthine/xanthine measured in tissue and plasma by a luminescence method

This simple method for sequentially quantifying hypoxanthine (HYP), inosine (INO), and adenosine (ADN) concentrations exploits the H2O2 peroxidase-catalyzed chemiluminescence of luminol. Though applied here only to tissue and plasma, this method can be adapted to analyze other body fluids. HYP in human plasma was stable for 30 min in 10 mmol/L EDTA reagent, whereas ADN was slowly converted to INO. Analytical recovery of HYP and INO added to plasma was 102% each; that of ADN was 95%. The within-run mean CVs for determinations of HYP, INO, and ADN at 1 mumol/L were 3.46%, 2.65%, and 3.01%; at 10 mumol/L they were 2.16%, 1.88%, and 1.63%, respectively. Corresponding between-run CVs were 5.34%, 4.09%, and 4.17%; and 3.43%, 2.40%, and 2.88%, respectively. Bilirubin at a concentration greater than 50 mumol/L interferes, but this interference is eliminated by bilirubin oxidase. Results for both tissue and plasma are compared with previously published results based on different analytical methods.

Biochemical evaluation of fetus with hypoxia caused by severe preeclampsia using cordocentesis

Biochemical evaluation of the fetus using cordocentesis was performed in sixteen pregnant women with severe preeclampsia. In addition, FHR monitoring and Doppler flow velocimetry of the umbilical artery were examined in these cases before the cordocentesis. Other than blood gas and routine hematologic and biochemical examinations, catecholamine and hypoxanthine concentrations were also evaluated in some cases. According to the results it is obvious that the fetus of mother with severe preeclampsia is exposed to hypoxemia with the delta pO2, the difference from the mean in each gestation, of -22 mmHg. Especially, the prognosis of the severely growth-retarded babies with pO2 below 10 mmHg, or delta pO2 30 mmHg lower than the mean standard value, is poor. Among 16 babies, 4 with severe hypoxia or acidosis and growth retardation died perinatally. In contrast, severely growth-retarded babies without hypoxia or acidosis were alive. Since neither FHR monitoring nor Doppler velocimetry always reflect biochemical values of the fetus of a severe preeclamptic mother, hence the precise evaluation of fetal condition using cordocentesis is indispensable to determine the timing of the delivery and to prevent the neurological sequelae caused by hypoxia, especially when the fetal growth is retarded.

Hypoxanthine phosphoribosyltransferase activity in tissues and hypoxanthine concentrations in plasma and CSF of the horse in comparison with other species

1. Plasma hypoxanthine and xanthine concentrations are very low in the horse and low in rat, mouse and greyhound compared to concentrations in beagles, man, sheep and rabbit. 2. Activities in erythrocytes of the main enzyme metabolizing hypoxanthine, hypoxanthine phosphori-bosyltransferase, show a similar pattern (Tax et al., 1976, Comp. Biochem. Physiol. 54B, 209-212); thus low activities have been found where plasma concentrations were low. 3. Hypoxanthine phosphoribosyltransferase activities in horse tissue other than erythrocytes are similar to those in man and rabbit with high activities in brain; this enzyme may therefore be functionally important in equine brain.

[Analysis of uric acid and oxypurines in normal subjects and in gout patients]

The behavior of plasma and urine oxypurines (hypoxanthine and xanthine) and of uric acid has been studied in normal subjects and in gout patients. Oxypurines and uric acid were increased in the plasma of gout patients but only the urinary excretion of hypoxanthine was higher in this group. The interpretation of the observed variations is discussed.

[Clearance of oxypurines in normal subjects and in gout patients subjected to a purine-free diet. Effects of allopurinol]

The clearance of uric acid, hypoxanthine and xanthine has been examined in gout patients and in normal subjects compared to creatinine, after a purine-free diet. The treatment decreased the clearance in normal subjects, but showed an opposite effect in gout patients. The clearances both of uric acid, hypoxanthine and xanthine were enhanced by allopurinol. The interpretation of the observed variations is discussed.

The metabolic relation between hypoxanthine and uric acid in man following maximal short-distance running

This study was performed to assess the metabolic relation between hypoxanthine and uric acid following short-distance maximal running. Eleven trained males, mean age 22 years (16-31), were instructed to run 800 m in the shortest time possible. Blood samples were collected before warm-up, before the run, immediately after the run and periodically up to 24 h following the run. Blood lactate was determined after warm-up, and at 5, 10, and 30 min following the run. Mean VO2 max for the subjects was 65.8 (4.7) (SD) ml kg-1 min-1 and mean oxygen demand for the running was 118 (8)% of VO2 max. Plasma hypoxanthine levels rose from 3.3 (1.4) to a peak of 48.2 (19.0) mumol l-1 at 20 min following the run and at 180 min had almost returned to pre-run levels. Plasma uric acid levels rose from a pre-run value of 267 (34) to a peak value of 431 (87) mumol l-1 at 45 min following the run. Uric acid concentrations had not returned to normal at 10 h following the run. The blood lactate level peaked at 5 min with 13.7 (2.0) mmol l-1. The results obtained in this study indicate a metabolic relationship between the formation of hypoxanthine and the formation of uric acid. The data also indicate that xanthine oxidase is active following short-distance intensive running.

Uricosuric effect of irtemazole in healthy subjects

Following a single dose of 50 mg irtemazole per os, plasma uric acid levels decreased after 1 h and fell to 53.5% of the original value within 6-12 h. Renal uric acid excretion increased up to 66 mg/h 30 min after drug application and reached its maximum of 151 mg/h 30 min later. Uric acid clearance also increased after 30 min and reached its maximum of 56 ml/min after 60 min. The response of the kidney to irtemazole is faster than to benzbromarone or probenecid. Lowering of plasma uric acid has a shorter-lasting effect than benzbromarone or probenecid. At 24 h after the application of 50 mg irtemazole the decrease of the plasma uric acid was between 15.4% and 30.0%, or 24.7% on average. Three days after the application the basic plasma uric acid levels were reached again.

Effect of probenecid on oxypurines in plasma

Probenecid decreased the plasma concentration of oxypurines (hypoxanthine and xanthine) but did not increase the renal excretion of oxypurines. However, the concentrations of hypoxanthine and nucleotides (inosine monophosphate, adenosine monophosphate, adenosine diphosphate, adenosine triphosphate, guanosine diphosphate and guanosine triphosphate) in red blood cells did not change after the administration of probenecid. In addition, the drug did not inhibit adenosine deaminase, purine nucleoside phosphorylase, hypoxanthine guanine phosphoribosyl transferase and xanthine oxidase in vitro. These results suggested that the rapid fall of plasma concentration of uric acid due to the potent uricosuric action of probenecid resulted in the fall of plasma concentration of oxypurines.

[The assessment of the safety of vacuum extraction deliveries under routine epidural block]

To assess the safety of vacuum extraction (V.E.) deliveries under continuous lumbar epidural block (E.B.) with Bupivacain, the modified Krebs score in CTG, Apgar score, cord arterial blood acid-base balance, hypoxanthine, CPK, CPK-BB, Neuron specific enolase and c-AMP were examined. A total of 74 full term oxytocin-induced labors were divided into three groups: A) 21 cases by V.E. under E.B., B) 34 cases under E.B. only, and C) 19 cases without V.E. or E.B. There was no difference in age, gestational weeks in the three groups. However, the incidence of primiparas was highest in group A. Though CTG showed a temporary low Krebs score in group A within 30 minutes after the initiation of E.B., it was found that there was no significant difference between the three groups 30 minutes before parturition. The apgar score, cord arterial blood pH, PO2 and B.E. were also found to be similar in all three groups. Among various kinds of substances in the cord blood, both CPK-BB and c-AMP showed a striking rise in group A, compared to groups B and C. Therefore, the use of V.E. under E.B. might be hazardous to the well-being of the newborn infant.

[Behavior of plasma and urine purines, after a purine-free diet, in normal subjects and patients with gout]

Plasma and urine oxypurines (hypoxanthine and xanthine) and uric acid, were evaluated in normal subjects and in gouty patients before and after a purine free diet. After a 7-days period, plasma oxypurines were remarkably higher in normal subjects, while they did not undergo variations in gouty patients, which showed higher in basal conditions. No significant changes in urinary excretion were observed in both cases. The interpretation of the observed variations is discussed.

[Plasma hypoxanthine and intraerythrocytic ATP in umbilical cord blood as markers of perinatal hypoxia]

We determined blood pH, plasma hypoxanthine (Hx) and intraerythrocyte ATP (iATP) concentrations in umbilical cord blood from 20 normal newborn infants (10 delivered by the vaginal route and 10 by caesarean section) and in 18 newborns with clinical signs of perinatal asphyxia (9 with meconium stained amniotic fluid and 9 with fetal bradycardia). Blood pH was significantly lower in infants with clinical signs of perinatal asphyxia (p less than 0.01). Four newborns with meconium or bradycardia had pH values within normal control levels. Hx concentrations were lower in infants delivered by caesarean section with respect to normal infants born by the vaginal route (p less than 0.05). Newborns with meconium or fetal bradycardia showed Hx concentrations higher than normal newborns (p less than 0.01), but 2 infants with signs of perinatal hypoxia had Hx levels within the normal newborn range. All babies with meconium or bradycardia had an iATP concentration lower than control infants (p less than 0.01). These results indicate that: the pH and Hx determinations in the newborn may underestimate hypoxia and, that measurement of iATP may be useful parameters to asses perinatal hypoxia.

Apparent inosine uptake by the human heart

Although inosine has been used clinically to support the myocardium, no data are available on the fate of exogenous inosine in the human heart. We therefore infused six patients, catheterised for coronary angiography, with inosine (5 mg.kg-1.min-1 intravenously) for 6 minutes. Before infusion, the arterio-venous difference of inosine, hypoxanthine and xanthine across the heart was nil. During infusion, arterial inosine increased substantially, exceeding the coronary sinus concentration by a maximum of 200 (SEM 53) mumol.litre-1, p = 0.02, at the fourth minute. Arterial hypoxanthine and xanthine also increased, while the arterio-venous difference became 16(11) and 10(3) (p = 0.04) mumol.litre-1, respectively. Left ventricular dP/dtmax increased by 22(7)% (p = 0.04) at the end of infusion. Thus, there seemed to be substantial uptake of inosine by the human heart, followed by improvement in haemodynamics.

Influence of peripheral arterial occlusive disease on muscular metabolism. Part 1: Changes in lactate, ammonia, and hypoxanthine concentration in femoral blood

The concentrations of lactate, ammonia and hypoxanthine were determined in blood from the femoral artery, femoral vein and cubital vein under resting conditions in 23 patients with stage II, 10 patients and 20 diabetics with stage IV peripheral arterial occlusive disease (PAOD) and in 19 healthy subjects. The metabolite concentrations were also measured immediately and 20 min after calf exercise in the patients with stage II PAOD and in the controls. At rest, there was a negative arteriovenous difference in femoral lactate level and a positive arteriovenous difference in the ammonia level in all groups. After exercise to the claudication limit, the femoral venous concentration and arteriovenous difference for lactate increased in the patient group significantly higher than in the controls, who were exercised three times as heavily. Furthermore, there was a significant rise in femoral venous ammonia concentration with inversion of the arteriovenous difference into the negative range and an increase in femoral venous hypoxanthine concentration only in the patients with PAOD and not in the controls. A significant correlation was found between the exercise-induced increases in lactate and ammonia. The results indicate activation of the purine nucleotide cycle in the muscles of limbs with impaired circulation, even for a short duration of load. This can be explained by activation of the AMP-deaminase in type I and type IIa muscle fibres by anoxaemia. The purine nucleotide cycle has an emergency metabolic function in ischaemia to maintain muscle contractility. Ammonia determination in femoral blood permits, in association with lactate and hypoxanthine determination, a precise quantitative assessment of the metabolic effects of PAOD.(ABSTRACT TRUNCATED AT 250 WORDS)

A new case with hereditary xanthinuria: response to exercise

The concentration of purines in plasma and urine from a 37-yr-old healthy man with a very low plasma urate concentration was measured by HPLC. A persistent increase in xanthine and a slight elevation of hypoxanthine was found. The metabolic response to intensive treadmill running and long distance running was investigated. The hypoxanthine concentration increased to about the same level as in healthy controls, but the elimination from plasma was considerably slower. The high xanthine level was practically unchanged by exercise.

Plasma metabolic disturbances and reperfusion injury following partial limb ischaemia in man

Despite efficient revascularisation procedures for vascular disease, the limb can occasionally be lost following reperfusion. One contributing factor might be the formation of oxygen free radicals. This study attempts to describe the conditions necessary for oxy-radical formation from adenine nucleotide breakdown products and the role of plasma creatine content as a marker of cellular injury. Twelve patients undergoing aortic reconstructive surgery were studied. Only partial ischaemia of the lower limbs was induced by the aortic clamping, since varying degrees of collateral circulation existed. Radial arterial and external iliac venous blood was obtained simultaneously before, during and after cross-clamping of the aorta, and plasma levels of ATP, ADP, hypoxanthine, phosphocreatine, creatine, creatinine and lactate measured using luminescence and spectrophotometry. Venous creatine content increased during ischaemia and was doubled 30 min after recirculation. This increase was possibly due to leakage following cellular injury agreeing with a previously observed decrease in muscle tissue creatine content. The iliac arterio-venous difference of hypoxanthine and lactate markedly increased immediately post-ischaemia, while the phosphocreatine difference decreased. Plasma hypoxanthine was abundant in the leg on reoxygenation. The existence of a xanthine oxidase system in skeletal muscle could produce favourable conditions for oxy-radical formation through hypoxanthine degradation, which may contribute to the known muscle tissue injury.

High-performance liquid chromatographic evaluation of PCF 39, a new immunomodulator agent

An high-performance liquid chromatographic analysis of PCF 39, N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine, with ultraviolet detection, has been devised and validated. The main pharmacokinetic results encountered for rats treated intravenously with PCF 39 at a dose of 100 mg/kg are described.

[Purine transport through the blood-brain barrier in hypoxanthine phosphoribosyltransferase deficiency]

The transfer of purines through the hematoencephalic barrier is poorly understood. Allopurinol inhibits the enzyme xanthine oxidase and increases xanthine and hypoxanthine plasma levels, but it should not increase the cerebrospinal fluid (CSF) levels of these purines owing to the absence of xanthine oxidase in the central nervous system (CNS). In the present study we evaluated the plasma and CSF concentrations of uric acid, hypoxanthine, xanthine and inosine in the baseline state and after 7 days of allopurinol administration (5-10 mg/kg/24 h) in 4 patients with hypoxanthine phosphoribosyltransferase (HPRT) deficiency. The CSF uric acid level was positively correlated with its plasma level (r = 0.93, p less than 0.01). The CSF hypoxanthine and xanthine concentrations were, as a mean, 5 and 2 times higher, respectively, in patients with HPRT deficiency than in 4 control individuals. As hypoxanthine basically comes from adenine nucleotides, while xanthine comes from guanine nucleotides, this finding suggests that in the CNS of patients with HPRT deficiency there is a higher degradation level of adenine nucleotides than of guanine nucleotides. Allopurinol increased plasma concentration of hypoxanthine, xanthine and inosine 4, 10 and 3 times, respectively, in relation to baseline values. In CSF, the mean increase of hypoxanthine and xanthine concentration was 17.5 mumol and 7.7 mumol, respectively, whereas inosine level was unchanged. These results suggest that in HPRT deficiency hypoxanthine and xanthine may be transferred to the brain.

[Purine metabolism in human tumors]

Levels of oxypurines (hypoxanthine and xanthine) and uric acid were measured in plasma and urine of tumor bearing patients (gastric and colon rectal tumors), and of subjects affected by non specific diseases. In both groups, an increase in plasma purine bases and a decrease of their excretion was observed as compared to healthy controls; no substantial variations concerning uric acid were found. Possible mechanisms inducing alterations of purine metabolism in so different conditions are discussed.