Acetylation phenotypes and environmental chemical exposure of people with idiopathic systemic lupus erythematosus.

OBJECTIVE: To test the hypotheses that there is an excess percentage of slow acetylators among patients with idiopathic systemic lupus erythematosus (SLE) and that these patients had excessive exposure to environmental amines and hydrazines before the onset of illness. METHODS: Case-control study with structured interview and acetylation phenotyping. RESULTS: No excess proportion of slow acetylators or environmental amine exposure was found. CONCLUSION: Slow acetylation phenotype and exposure to environmental amines are not principal causes of idiopathic SLE.

Determination of gossypol enantiomers in plasma after administration of racemate using high-performance liquid chromatography with precolumn chemical derivatisation.

A high-performance liquid chromatographic assay with precolumn chemical derivatisation was developed for the determination of gossypol enantiomers in plasma, after administration of the racemate. Racemic gossypol acetic acid in plasma was extracted into acetonitrile and analysed using a reversed-phase column and a coulometric detector in the redox mode. To separate the enantiomers, 30 microliters of the chiral derivatising reagent, (R)-(-)-2-amino-1-propanol (50 mg/ml) and 15 microliters of 20% (v/v) acetic acid were added to the acetonitrile layer which was then heated at 60 degrees C for 100 min. The mobile phase used to resolve the derivatised enantiomers was 0.2 M phosphate buffer (pH 3.5)-acetonitrile (38:62, v/v). At a flow-rate of 1.5 ml/min, the retention times for derivatised (+)-gossypol and (-)-gossypol were 4.0 and 7.8 min, respectively. Two cancer patients received 10 mg racemic gossypol acetic acid three times a day. In one patient, the racemic, (+)- and (-)-gossypol acetic acid plasma concentrations after 65 days of therapy were 317, 213 and 104 ng/ml, respectively. In the other patient, these values were 362, 210 and 152 ng/ml, respectively, after a week of therapy. This represents, to our knowledge, the first determination of the individual enantiomer levels of gossypol after administration of the racemate.

Gossypol and Na+, K+ ATPase from human erythrocytes.

The inhibition of Na+, K+ ATPase by gossypol has been proposed as a mechanism for the hypokalemia occurring in some patients receiving this drug. Gossypol acetic acid, 3 microM (higher concentration than present clinically), did not inhibit this enzyme prepared from erythrocytes from 5 humans. Thus, it is unlikely that gossypol inhibition of the usual form of this enzyme is the mechanism for the initiation of the hypokalemia.

PIP: Whether gossypol inhibits the enzyme Na+,K+ ATPase, in human red blood cell membranes, a theory proposed to account for the low calcium levels seen in people who take gossypol, was tested. In volunteers taking 30 mg racemic gossypol, gossypol levels of 40 ng/ml (-enantiomer) and 100 ng/ml (+ enantiomer) were detected. In this experiment, the initial gossypol acetic acid concentration was 1.8 mcg/ml (3.1 mcM). The ATPase assay of erythrocyte membranes involved an assay for inorganic phosphate released, controlling for the ouabain-sensitive ATPase activity. Gossypol did not inhibit ATPase in erythrocytes from any of 5 volunteers, including 2 subjects of Chinese ancestry and 3 of European stock. Thus it is unlikely that inhibition of ATPase from red blood cells, the usual form of this enzyme, initiates hypokalemia.

Hydromorphone levels and pain control in patients with severe chronic pain.

To better understand the use of narcotic analgesics, the hydromorphone concentration was measured in serum samples from 43 patients with chronic severe pain who were receiving this drug. At the time of blood sampling, pain intensity, mood, and cognitive performance were assessed. There was large individual variation in the dose-drug level relationship. Seven patients with bone or soft tissue pain and drug levels of greater than or equal to 4 ng/ml had good pain control, whereas 10 did not. None of 15 patients with levels less than 4 ng/ml had pain control, despite drug doses similar to those given patients with higher levels. Thus 60% of the patients without control of their pain had hydromorphone levels below the lowest level that produced pain control. No patient with pain from nerve infiltration or compression had good pain control, irrespective of the drug level or dose. Poor mood correlated with high pain intensity and low drug level. Impaired cognitive performance was not related to drug level. Knowing that there is a low concentration of narcotic in the blood of a patient with chronic severe pain who is receiving high drug doses and who shows lack of both efficacy and side effects may reassure health care professionals that further narcotic dosage escalation is appropriate.

Dose-dependent induction of anti-native DNA antibodies in cats by propylthiouracil.

Cats receiving propylthiouracil (PTU) develop antinuclear antibodies (ANA) and an immune-mediated disease syndrome characterized by anorexia, lymphadenopathy, weight loss, and Coombs-positive hemolytic anemia. Investigation of the ANA specificity indicated that the predominant ANA activity consistent of anti-native DNA (nDNA) antibodies. The formation of anti-nDNA antibodies and immune-mediated disease syndrome appeared to be dose-dependent, even in cats in which a response had been induced on 4 prior occasions. These results supply further evidence that PTU-induced autoimmunity is not the result of a simple drug allergy. Rather, it appears that PTU induces a lupus-like syndrome, including the hallmark sign of systemic lupus erythematosus, anti-nDNA antibodies.

A nonradioactive iothalamate method for measuring glomerular filtration rate and its use to study the renal handling of cibenzoline.

A high-pressure liquid chromatographic method was developed to measure nonradioactive iothalamate in serum and urine for use in estimating glomerular filtration rate (GFR). This method was used to study the renal handling of cibenzoline, an experimental antiarrhythmic drug. The mean cibenzoline clearance was 3.5 +/- 2.5 (SD) times the glomerular filtration rate. The clearance of non-protein-bound cibenzoline was seven times GFR, indicating excretion by the renal tubular secretory pathway for organic bases. This drug, at the doses used, did not lower creatinine clearance, indicating that the effect of basic drugs competing with creatinine for the base secretory pathway appears to be dose and drug dependent.

Accumulation of polyamines and their weak association with lower body temperature in elderly convalescent patients.

Because spermine and spermidine have caused hypothermia in rodent experiments, we tested the hypothesis that these polyamines accumulate in some elderly convalescent patients and that this accumulation could predispose to lower body temperature. Fourteen healthy young, seven healthy older, and 47 convalescent elderly subjects had serum spermine and spermidine concentrations measured by high-pressure liquid chromatography. The mean +/- SD spermine values were 18 +/- 10, 24 +/- 15, and 40 +/- 54 ng/ml, respectively. The values for spermidine were 28 +/- 10, 38 +/- 29, and 76 +/- 46 ng/ml, respectively. The differences between the young and convalescent elderly were statistically significant for both compounds. Rectal temperatures were measured in 39 elderly convalescent subjects with a thermometer designed for accuracy at low temperatures. These subjects were stratified into a warm and cool half based on a median rectal temperature of 37 degrees C. There was an association between having high spermine levels and being in the cool half of the elderly convalescent group (P less than 0.05). We conclude that some elderly convalescent patients have high levels of spermidine and spermine and that these high spermine levels may be associated with lower body temperature.

Pharmacokinetics of pentobarbital enantiomers as determined by enantioselective radioimmunoassay after administration of racemate to humans and rabbits.

Radioimmunoassays were developed for R- and S-pentobarbital. The optical isomers of pentobarbital were individually alkylated to N-crotonic acid analogs that were coupled to bovine serum albumin. Immunization of rabbits with the conjugates, which were enantiomerically pure at the asymmetric' carbon of the pentobarbital moiety, led to formation of antisera that selectively bound the predicted enantiomer. In displacement studies with enantiomerically pure radioligands, the opposite enantiomer showed 1.0 to 1.4% cross-reaction. Similar selective binding was observed for enantiomers of secobarbital, thiopental and thiamylal. Assays were developed and used to determine enantiomer pharmacokinetics in rabbits and humans given racemic pentobarbital. In rabbits, difference in clearance of the two isomers was minimal, the result of a slightly larger volume of distribution of the R-enantiomer combined with a slightly higher value of the elimination rate constant beta for the S-enantiomer. In humans, the volume of distribution was 12% greater for the R-enantiomer, but the value of beta was 14% higher for this isomer as well. Thus, the median clearance of the S-enantiomer (1.96 liters/h) was 25% less than that of the R-isomer (2.58 liters/h). The S-enantiomer was also more strongly protein bound in plasma (73.5% vs 63.4% for the R-enantiomer), which is consistent with its structural congruence to S-warfarin, S-phenprocoumon and S-glifumide.

Lipophilicity, hydrophilicity, and the central nervous system side effects of beta blockers.

One of the attributes of beta-adrenergic blocking agents that has distinguished these drugs from each other is degree of lipophilicity. While this feature may play a role in facilitating passage across the blood-brain barrier, it is essential to realize that crossing the barrier is not necessarily synonymous with the ability to cause central nervous system (CNS) effects. Several studies have found some degree of CNS side effects, particularly tiredness and fatigue, with atenolol, a hydrophilic beta blocker. Pindolol, a moderately lipophilic beta blocker, has been reported to cause greater disturbances on electroencephalogram (EEG) than propranolol, the most highly lipophilic beta blocker. The investigational agent bevantolol exhibits a moderate degree of lipophilicity and a low frequency of CNS side effects. Drug-induced increases in plasma catecholamine levels, the possible saturation of CNS receptor sites at relatively low drug levels, and the specific structural details of beta-blocker molecules have been suggested as possible contributory factors in determining the degree of CNS effects.

Procainamide, N-acetylprocainamide, antinuclear antibody and systemic lupus erythematosus.

Long-term therapy with procainamide (PA) leads to the systemic lupus erythematosus syndrome (SLE) in about 30% of patients and 80% develop antinuclear antibodies. Acetylation of procainamide results in the formation of N-acetylprocainamide (NAPA) the propensity of which to induce SLE and to increase antinuclear antibodies is negligible while its antiarrhythmic properties remain. Slow acetylators of PA have a greater tendency to induce SLE consistent with the observation that it is the level of PA that is responsible for the observed immunologically-mediated side effects of the compound. This is also suggested by the remission of PA-induced SLE when PA is replaced with NAPA for the control of cardiac arrhythmias. Thus, NAPA, compared to the parent compound, has little tendency to induce SLE.

Stereoselective renal tubular secretion of quinidine and quinine.

Quinidine and quinine are stereoisomers. When given sequentially or simultaneously, the renal clearance of values of quinidine and quinine were measured in seven healthy volunteers and when given simultaneously, to an additional five elderly men. Analytic specificity was provided by an HPLC drug assay. Protein binding was measured by equilibrium dialysis. The quinidine clearance exceeded the quinine clearance in every individual. The mean (+/- SD) ratio of these clearances was 4.2 +/- 1.4 when the drugs were given together and 4.4 +/- 2.3 when they were given separately in the younger subjects and 3.4 +/- 0.5 when given simultaneously to the elderly. Calculating clearance of drug in serum water (unbound drug clearance) revealed a quinidine clearance of 6.1 +/- 2.3 times that of creatinine measured simultaneously, and for quinine it was 1.5 +/- 0.6 times that of creatinine. We conclude that there is stereoselective net renal tubular secretion of quinidine over quinine indicating stereoselectivity of this renal tubular transport process.

Propylthiouracil-induced immune-mediated disease in the cat.

An immune-mediated disease was produced in 9 of 17 (53%) normal healthy cats by daily p.o. administration of 150 mg of 6-propylthiouracil (PTU). This disease syndrome is characterized by lethargy, weight loss, lymphadenopathy, hemolytic anemia, a positive direct antiglobulin test (DAT) and antinuclear antibodies (ANA). The duration of drug administration before the development of a positive DAT and/or ANA ranged from 3 to 8 weeks (Mean +/- S.E.M. = 4.5 +/- 0.6), whereas the duration before the onset of clinical signs ranged from 4 to 8 weeks (6.1 +/- 0.6 weeks). On cessation of PTU administration, clinical signs resolved in all cats within 2 weeks, and the DAT and test for ANA were negative within 1 to 4 weeks (1.9 +/- 0.4 weeks). During nine PTU-rechallenge periods in four cats, both the mean time to develop a positive DAT and ANA (2.5 +/- 0.8 weeks) and the mean time to develop overt clinical signs (2.6 +/- 0.7 weeks) were shorter than similar mean times in the initial PTU treatment period (P less than .01). During nine episodes of PTU-induced disease in seven cats, PTU administration was discontinued and replaced with 150 mg of 6-propyluracil (PU), a nonsulfur analog of PTU. Resolution of both clinical and serologic signs of disease occurred in seven of the nine disease episodes within 1 to 3 weeks (2.1 +/- 0.4 weeks). In the two cats whose disease did not resolve on PU, one was sacrificed after 1 week of PU administration, without clinical or serologic resolution, because of the severity of the PTU-induced disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased urinary enzyme excretion in workers exposed to nephrotoxic chemicals.

Nephrotoxic chemicals are commonly present in the environment, particularly in the workplace. The level of occupational exposure to these chemicals has been so reduced that exposure to these agents now rarely causes clinically evident acute renal disease. A sensitive indicator of renal injury, urinary excretion of N-acetyl-beta-glucosaminidase, was utilized to evaluate persons exposed in the workplace to lead, mercury, or organic solvents, for evidence of renal effects from this exposure. None of the persons had clinically evident renal disease by history, none had hypertension, and all had normal findings on urinalysis. When compared with appropriate control populations, workers exposed to lead, workers exposed to mercury, and two of three groups of workers exposed to organic solvents had significant increases in urinary acetyl glucosaminidase activity. The third group of laboratory workers with low exposure to organic solvents had no increase in urinary acetyl glucosaminidase activity. It is concluded that exposure to environmental nephrotoxins at levels currently considered safe can produce renal effects as manifested by elevations of urinary acetyl glucosaminidase excretion. It is speculated that these renal effects are not always innocuous.

Pubertal changes in net renal tubular secretion of digoxin.

To evaluate the effect of puberty on the net renal tubular secretion of digoxin, we measured the ratio of digoxin clearance to creatinine clearance in 23 patients aged 4 to 21 yr and correlated this ratio with both sexual maturity (Tanner stage) and chronologic age. All subjects were at steady-state levels for digoxin treatment; all had normal serum creatinine values for age as well as normal serum potassium levels. Mean ratio for immature children (n = 14, Tanner 1 through 3.5) was 1.45 +/- 0.66. Mean ratio for mature adolescents (n = 9, Tanner 4 through 5) was 0.95 +/- 0.28. The difference between the two groups was significant (P less than 0.05). When patients were regrouped by age using either 13 or 15 yr as a cutoff, the difference in ratios was no longer statistically significant. Based on 45 subjects (new and from our previous study) aged 2 mo to 80 yr, there was a significant decrease in the clearance ratio with increasing age, but when the 23 subjects aged 4 to 21 yr were analyzed separately, the correlation between ratio and age was not significant. It appears that the decrease in net renal tubular secretion of digoxin from childhood to adulthood correlates better with full sexual maturation at puberty (Tanner 4 through 5) than with chronologic age. This observation may represent a developmental change in pharmacokinetics with broader significance than for digoxin disposition alone.