Two gold compounds, gold sodium thiomalate (AuTM) and auranofin (AF) are presently in clinical use in therapy of rheumatoid arthritis. The effects of varying doses of AF administered to rats by either the p.o. or the i.p. route on heme metabolism were determined. Twenty four hours after a single dose of AF, decreases in the sulfhydryl-containing enzymes, delta-aminolevulinic acid dehydratase and ferrochelatase activities were observed in the liver and kidneys. These decreases in heme biosynthetic enzymes were accompanied by decreases in cytochrome P-450-dependent enzymic activities and increases in microsomal heme oxygenase activity. These changes were observed with AF dosages as low as 5 mg/kg, with maximal changes occurring at a p.o. dose of about 15 mg of AF per kg and an i.p. dose of 5 to 10 mg of AF per kg. Dose-response studies with AuTM showed that maximal changes in heme metabolism occur at a lower dose of AF than of AuTM, even though AF was administered p.o. and AuTM was administered parenterally. In addition, the kidneys appeared to be more susceptible to the inhibitory effects of the two chrysotherapeutic agents than did the liver. The present studies demonstrate the p.o. drug AF affects heme metabolism in a manner similar to that reported previously with the parenterally administered AuTM.

Gold compounds are used clinically in rheumatoid arthritis therapy. Acute renal toxicity is observed in some patients receiving chrysotherapy. The present study addresses morphofunctional and biochemical changes in rat kidneys during the first 8 days following a single ip injection of gold sodium thiomalate (Au TM), one of the gold compounds presently in clinical use. Compared to controls, AuTM pretreatment resulted in increased urine output and elevated serum creatinine and urea nitrogen concentrations. Also, by Day 8, treated rats had decreased body weights and increased kidney weights. Postmortem examination on Day 1 showed pale and mottled kidneys and diffusely pale inner cortex. Microscopically, there was severe coagulative necrosis of the proximal tubular epithelium. Epithelial regeneration was prominent by Day 4 and was nearly complete by Day 8. The regenerating epithelium was hyperplastic with basophilic cytoplasm and pleomorphic nuclei. Alterations in renal heme biosynthesis and drug metabolism paralleled the morphologic changes. The activity of δ-aminolevulinic acid dehydratase and benzo[a]pyrene hydroxylase were inhibited on Days 1, 2, and 4 following AuTM administration. Decreases in monooxygenase activity were accompanied by decreases in renal cytochrome P-450 levels. In contrast, renal microsomal heme oxygenase activity was elevated 9.5-fold on Day 1 and 2.5-fold on Day 2. By Day 8, all renal enzymatic activities assayed for were similar to those obtained with untreated rats.

In rhesus monkeys, in which porphyria was induced by the administration of allylisopro-pylacetamide (AIA), hepatic δ-aminolevulinic acid synthase (ALA-S) was increased. Cytochrome P-450 and associated monooxygenase activities and microsomal heme oxygenase activity were decreased in these animals. Administration of heme for 4 days concurrently with AIA prevented the induction of hepatic ALA-S but produced further decreases in cytochrome P-450 and monooxygenase activities. The decrease in heme oxygenase activity elicited by AIA alone was partially reversed. Administration of heme alone caused an impairment of hepatic drug metabolism but had no significant effect on heme metabolism. The porphyric monkeys showed elevation of porphyrin levels in blood and urine. When heme was administered concurrently with AIA, blood porphyrin levels were further elevated, while the urinary excretion of porphyrins was lower than that following treatment of monkeys with AIA. Following the administration of heme alone, blood and urinary porphyrin levels were minimally affected. These results suggest that repeated heme administration in the primate may adversely affect drug metabolism by the liver.

The effects of the PCBs mixture, Aroclor 1254, as modifiers of monooxygenases were studied in rabbits and mice. From data presented, it is not possible to generalize the biological effects of PCBs observed with rats, namely, that they are potent, nonspecific inducers of monooxygenase activities. This environmental pollutant enhanced microsomal drug-metabolizing enzymes in livers of rabbits and C57Bl/6J and DBA/2J mice. In rabbit lung, it inhibited, and in rabbit kidney, it enhanced the metabolism of ethylmorphine. Further, at dosages used, PCBs were poor inducers of aryl (benzo(a)pyrene) hydroxylase activity in livers of C57BL/6J and DBA/2J mice; they enhanced aryl hydrocarbon hydroxylase activity in rabbit kidney but caused a significant depression of its activity in rabbit lung. These studies demonstrate that the biologic impact of the widely distributed environmental pollutant, PCBs, may differ in different species and emphasize the need to carry out toxicological studies in more than one species of animals. The differential effects observed on various organs may also be important determinants of organ-targeted chemical toxicity.

The ability of honeybee venom to suppress Mycobacterium butyricum-induced arthritis was studied in Lewis rats. Bee venom, 2 mg.kg-1.day-1 for 24 days, suppressed but did not abolish the primary and secondary inflammatory responses to the adjuvant as monitored by decreases in the swelling of the left and right hind paws and adjuvant-induced arthritis on heme metabolism were also examined. Bee venom or adjuvant had no effect on hepatic delta-aminolevulinic acid synthase, porphyrin content, or ferrochelatase activity. However, with both treatments cytochrome P-450 and the associated enzymic activities of ethylmorphine N-demethylase and benzo[a]pyrene hydroxylase were depressed markedly. In contrast, both treatments caused several-fold enhancement of hepatic microsomal heme oxygenase activity. Adjuvant-treated rats receiving bee venom showed changes in heme metabolism which were of a magnitude similar to those observed when either agent was administered to the experimental animals. Although the bee venom appears to suppress adjuvant-induced arthritis to a greater extent in female than in male rats, the alterations in heme metabolism were similar in bee venom-treated male and female rats. The observed changes in heme metabolism elicited by the venom or by the adjuvant are strongly suggestive of perturbations of the immune system causing alterations in hepatic microsomal enzymes.

In rats pretreated with the PCBs mixture, Aroclor 1254, or with 3-methylcholanthrene, pulmonary cytochrome P-450 content was increased and benzo(a)-pyrene hydroxylase activity was markedly enhanced. In rabbits, 3-methyl-cholanthrene caused no significant increase in pulmonary cytochrome P-450 content but did cause a 2-fold induction of the hydroxylase activity. In contrast, PCBs caused a 45% decrease in rabbit lung cytochrome P-450 content, and a 31% decrease in the hydroxylase activity. Although PCBs are generally considered as powerful inducers of microsomal monooxygenases, the present studies provide evidence for species and tissue specific action of the PCBs.

Large interindividual differences occur in the in vivo metabolism of drugs due to genetic and environmental factors. Our studies show that intraindividual variabilities in rates of metabolism are relatively low for antipyrine and phenylbutazone, which are drugs that are primarily metabolized by the liver and have low hepatic extractions; whereas in the case of phenacetin, a drug that undergoes extensive metabolism in the gastrointestinal tract or during its first pass through the liver, or both, intraindividual variations in plasma half-lifes and areas under the plasma concentration-time curves are of much greater magnitude. In our studies, no effort was made to control the lifestyles of our subjects. The variations in rates of drug metabolism did not result from assay procedures, since there was little variation in measured concentrations when the drugs were added to plasma and assayed on multiple occasions. Intraindividual variation occurring in subjects given the drug on 5 different occasions may be due to changes in the external environment or changes in internal physiologic parameters or both. Our studies confirm the usefulness of antipyrine as a test drug in studying drug metabolism in man and also demonstrate that the antipyrine test may be able to detect those subjects whose environments are perturbed by unidentified factors.

In this study, the effects of the gold compound, gold sodium thiomalate, on the heme biosynthetic pathway, on cytochrome P-450-dependent monooxygenases, and on heme catabolism were examined. The addition of the gold compound, in vitro , resulted in the inhibition of hepatic δ-aminolevulinic acid dehydratase, NADPH-cytochrome c reductase, and ethylmorphine N-demethylase activities. There was also a slight decrease in cytochrome P-450 content. Gold was a noncompetitive inhibitor of both δ-aminolevulinic acid dehydratase and ethylmorphine N-demethylase activities. Gold sodium thiomalate, administered acutely, altered heme biosynthetic pathway enzymes in erythrocytes, liver, and kidney. Erythrocyte δ-aminolevulinic acid dehydratase activity was decreased with a concomitant increase in protoporphyrin content. In the liver δ-aminolevulinic acid dehydratase and ferrochelatase activities were significantly inhibited and the microsomal heme content was significantly decreased. In the kidney, the major site of gold deposition, the activities of δ-aminolevulinic acid synthase, δ-aminolevulinic acid dehydratase, and ferrochelatase were markedly inhibited and total porphyrin content was markedly decreased. After acute gold treatment, monooxygenase activities in liver and kidney were decreased. Cytochrome P-450 content of both tissues decreased significantly and ethylmorphine N-demethylase and benzo(a)pyrene hydroxylase activities were both inhibited. NADPH-cytochrome c reductase activity, however, was not altered. In contrast to its inhibitory effects on the heme biosynthetic pathway and cytochrome P-450-dependent monooxygenases, gold caused a 1.5- and 8-fold induction in the liver and kidney, respectively, of microsomal heme oxygenase activity, the rate-limiting enzyme in the catabolism of heme. There was no change in any of the parameters in the liver or erythrocytes after chronic treatment with gold. In the kidney, δ-aminolevulinic acid dehydratase activity and total porphyrins were significantly decreased. However, as in the liver, cytochrome P-450 content was not significantly altered. These results indicate that an adaptive response develops during chronic gold treatment which prevents the depression of heme biosynthesis and the formation of cytochrome P-450.