Effect of cis-diamminedichloroplatinum (II) on metallothionein induction and trace element metabolism in rats fed different amounts of dietary zinc

Recent studies have suggested that the induction of metallothionein synthesis in kidneys of mice by the acute administration of bismuth and other trace elements might protect against cis-diamminedichloroplatinum (II) nephrotoxicity. The present study was designed to determine the effects of dietary zinc and cis-diamminedichloroplatinum (II) on the induction of liver and kidney metallothionein and its subsequent effect on nephrotoxicity and trace element metabolism in rats. Male rats were fed diets containing 5, 20, 80, or 320 mg zinc/kg diet for 3 weeks. Each dietary group was subdivided into 3 groups. In one group, each rat received an i.p. injection of 7.5 mg cis-diamminedichloroplatinum (II)/kg b.w. All other rats received saline. During the next three days a second group of rats was pair-fed to the cis-diamminedichloroplatinum (II) injected group. A third group received no treatment and was allowed to eat ad libitum. Results showed that when dietary zinc was increased from 5 mg/kg diet to higher amounts, kidney metallothionein concentration increased twofold. cis-diamminedichloroplatinum (II) treatment increased kidney metallothionein even further, but elevated metallothionein gave no protection from the toxic effects of the drug. Serum copper concentration and ceruloplasmin activity were significantly lower with higher concentrations of dietary zinc, which indicated that these rats were mildly copper-deficient. There was a small but significant depression of superoxide dismutase activity and a highly significant increase in thiobarbituric acid reactive substances in kidneys of rats treated with cis-diamminedichloroplatinum (II) compared to either pair-fed or ad libitum controls. This supports the hypothesis that part of the mechanism for cis-diamminedichloroplatinum (II)-induced toxicity might be caused by free-radical generation. However, the data do not support the hypothesis that metallothionein induction protects the kidney from cis-diamminedichloroplatinum (II) toxicity.     

Trace element status and inflammation parameters during chronic indomethacin treatment in adjuvant arthritic rats

Oral indomethacin administration (2 mg/kg/d) was investigated in rats with adjuvant arthritis up to a period of 5 wk. Baseline low serum zinc levels in arthritic rats increased rapidly from the first week of indomethacin treatment (started 1 or 2 wk after disease induction), whereas baseline high serum copper decreased after 1–2 wk. After 3–4 wk of treatment, serum zinc levels returned to control values, but serum copper was somewhat higher in arthritic animals having received indomethacin 2 wk after disease induction than in controls. Clinical indices of inflammation simultaneously improved to reach control values at the end of the trial. Biological indicators of inflammation also improved, but did not reach control levels. Serum zinc correlated negatively with plasma fibrinogen (r=?0.69,p<0.005) and serum copper correlated positively with serum ceruloplasmin (r=0.92,p<0.0005) both in indomethacin-treated and untreated arthritic rats. Contrary to long-term glucocorticoid administration that was previously reported to maintain or aggravate hypozincemia, indomethacin treatment normalized perturbed zinc and copper status in arthritic animals.     

The CO2-SFE crude lipid extract and the free fatty acid extract from Perna canaliculus have anti-inflammatory effects on adjuvant-induced arthritis in rats

The anti-inflammatory (AI) activity of a supercritical fluid extract (CO(2)-SFE) of tartaric acid-stabilised Perna canaliculus mussel powder, and of the free fatty acid (FFA) class separated from the CO(2)-SFE extract by column chromatography, was investigated in the rat adjuvant arthritis model. Administration of the CO(2)-SFE extract (100 mg/kg BW/day s.c.) for 15 days post-adjuvant inoculation significantly reduced rear paw swelling by 34% and the deterioration in total body condition by 52% in arthritic rats, compared to vehicle controls. These observations were accompanied by a decreased serum ceruloplasmin oxidase activity, and reduced inflammatory response of the spleen. The mussel FFA extract given at one third of the dose (30 mg/kg BW/day s.c.) and for a shorter treatment period (5 days during the inflammatory phase) achieved an even greater AI activity, and was equipotent to piroxicam (2 mg/kg BW/day s.c.). Preliminary toxicology assessment using both arthritic and non-arthritic (healthy) rats revealed no significant differences between the mussel treatment groups and respective vehicle controls in either organ weights, tissue histology or selected biochemical parameters. These results indicate the CO(2)-SFE crude lipid extract and its FFA components from stabilised P. canaliculus mussel powder contain biologically significant AI activity in vivo, with no apparent adverse side effects.     

Kidney and liver metallothioneins in rats after administration of an organic compound

Intubation of rats with alpha-mercapto-beta-(2-furyl)-acrylic acid (MFA) for 5 days at 50 mg/kg caused a 7-fold increase in kidney copper concentration, a 2-fold increase in kidney zinc concentration, and a 20% increase in liver zinc concentration. The proteins which bound the increased metals were purified and identified as metallothioneins by their amino acid compositions. Two isoforms were isolated from each organ. Renal thioneins appeared identical to counterpart hepatic apoproteins, but the former bound Cu and Zn in a 2:1 mole ratio and the latter bound only Zn. Kidney contained over 10 times more metallothionein per g of tissue than did liver. In rats previously administered MFA, injection of cadmium sulfate resulted in rapid displacement of liver metallothionein-bound Zn by Cd under conditions where minimal metallothionein was found in Cd-dosed animals not administered MFA. We conclude that MFA induces metallothionein biosynthesis in kidney and liver of normal rats; this is a novel effect for an organic compound.     

Activities of fatty acid desaturases and fatty acid composition of liver microsomes in rats fed beta-carotene and 13-cis-retinoic acid

The fatty acid composition of microsomal lipids and the activities of delta 9- and delta 6-desaturases in liver microsomes of rats fed diets supplemented with beta-carotene and two levels of 13-cis-retinoic acid were studied. Four groups of male, weanling rats were fed semipurified diets containing 0 or 100 mg beta-carotene per kg diet, and 20 or 100 mg 13-cis-retinoic acid per kg diet. After 11 weeks of feeding, the rats were killed, liver microsomes were prepared and assayed for delta 9-desaturase and delta 6-desaturase activities. The activity of delta 9-desaturase was lower in liver microsomes of rats fed beta-carotene-supplemented diet or the diet supplemented with the higher level of 13-cis-retinoic acid. Microsomal delta 6-desaturase activity was, however, higher in liver of rats fed 13-cis retinoic acid; there was no effect of beta-carotene on delta 6-desaturase activity. The fatty acid compositional data on total lipids of liver microsomes were consistent with the diet-induced changes in fatty acid desaturases. Phospholipid composition of liver microsomes was also altered as a result of feeding beta-carotene or 13-cis-retinoic acid-containing diets. The proportions of phosphatidylethanolamine were generally higher, whereas those of phosphatidylcholine were lower in the experimental groups as compared with the control.     

Intestinal metallothionein and the mutual antagonism between copper and zinc in the rat.

A study has been made of the mechanism of the mutual antagonism between copper and zinc in rats. Dietary zinc concentrations of up to 450 mg/kg had no effect on intestinal 64Cu absorption but 900 mg/kg caused a 40% reduction. This was associated with an increase in the mucosal uptake of 64Cu in the small intestine. This occurred mainly in the form of metallothionein and it appeared that copper displaced zinc from the protein after its synthesis had been induced by zinc. Ths intestinal absorption of 65Zn was decreased by 20% when the dietary copper intake was increased from 3 to 24 mg/kg. Further increases in copper intake to 300 mg/kg did not cause any additional decrease in 65Zn absorption or any change in the association of intestinal 65Zn with metallothionein. Concentrations of this protein in the intestinal mucosa were not influenced by dietary copper intake.     

EFFECTS OF CHRONIC TREATMENT WITH AMINO-OXYACETIC ACID OR SODIUM n-DIPROPYLACETATE ON BRAIN GABA LEVELS AND THE DEVELOPMENT AND REGRESSION OF COBALT EPILEPTIC FOCI IN RATS

Abstract– Acute treatment of cobalt-induced epilepsy in rats with amino-oxyacetic acid (20-60 mg/kg intraperitoneally) resulted in a short period (30-90 min) of epileptic spike suppression. In contrast sodium n -dipropylacetate (100-400 mg/kg intraperitoneally) had no effect on spike frequencies. Chronic treatment of cobalt epileptic rats with amino-oxyacetic acid (2.5-10 mg/kg intraperitoneally daily) or sodium n -dipropylacetate (200-400 mg/kg intraperitoneally daily) elevated brain GABA concentrations significantly and reduced brain glutamate decarboxylase activity relative to control saline-injected cobalt epileptic rats. Brain γ-aminobutyrate aminotransferase activity was significantly reduced by chronic treatment with amino-oxyacetic acid, whereas chronic sodium n -dipropylacetate had no effect on brain γ-aminobutyrate aminotransferase activity although elevating brain GABA. Amino-oxyacetic acid (2.5-10 mg/kg intraperitoneally per day) reduced the frequency of epileptic spikes in the secondary foci of cobalt epileptic rats. The anticonvulsant action of amino-oxyacetic acid was most marked at 5 mg/kg intraperitoneally where a secondary focus failed to develop in treated cobalt epileptic rats. However, there was no simple relationship between the elevation of brain GABA and the anticonvulsant action of amino-oxyacetic acid. Thus focal GABA was higher in rats given intraperitoneal amino-oxyacetic acid (10 mg/kg) but the anticonvulsant action of amino-oxyacetic acid was less marked at this dose. Sodium n -dipropylacetate (200-400 mg/kg intraperitoneally per day) had no long-term anticonvulsant action in this model of epilepsy. It is concluded that the anticonvulsant action of sodium n -dipropylacetate, and probably that of amino-oxyacetic acid, is not likely to be mediated through a mechanism involving elevation of brain GABA.     

Induction of metallothionein by exposure to normobaric 100% oxygen atmosphere in rats with different zinc supply

The objective of this study was to determine the effects of an oxygen enriched environment on the induction of the metalloprotein metallothionein (MT) and its relation to zinc metabolism in rats supplied with different levels of dietary zinc. Male albino rats were fed purified diets based on maize starch, egg white, saccharose and soybean oil differing in the concentration of zinc (1; 20; 100; 500 mg Zn/kg diet). At a dietary zinc supply of 1 mg/kg, the rats developed a zinc deficiency indicated by visual and biochemical parameters. At the end of the 37-day feeding period, half of the rats were exposed to 100% oxygen for 12 h.

The oxygen treatment significantly reduced plasma zinc in the zinc supplemented rats and reduced it in tendency in the zinc deficient rats. The MT concentration was increased in the zinc supplemented groups in the liver, kidney and lung. The oxygen treatment elevated the metallothionein concentration in the two high zinc supplemented groups (100 and 500 mg Zn/kg diet) in the liver. The response of the zinc concentration in plasma and of hepatic metallothionein levels to oxygen exposure indicates a role of metallothionein in zinc distribution or interactions with other trace elements to support antioxidant capacity, rather than an impact on direct scavenging activity of free radicals.     

The effects of cadmium and copper on the renal uptake and metallothionein binding of gold in the rat and hamster

Rats and hamsters, (pre)-treated with copper and cadmium, were used to investigate whether species-differences in renal metallothionein synthesis in response to gold were determined by changes in the kidney concentrations of other metals. The effects of both dietary copper limitation and excess on the renal metabolism of gold also were studied in the rat. In this species, all of the pre-treatments affected the renal concentrations of total and metallothionein-bound copper, but none of them altered either the kidney uptake or thionein-binding of gold. Incorporation of zinc into the metallothionein, which accompanied the binding of gold in this fraction of the kidney, however, was influenced slightly by the pretreatments. In hamsters, pretreatment with cadmium, which increased the concentrations of total and thionein-bound zinc in the kidneys, also did not affect the renal uptake of gold, although it increased significantly the binding of gold to the metallothionein fraction of the renal cytosol. This increased binding of gold also was accompanied by further increases in the zinc and copper contents of the metallothionein; the contents of total and thionein-bound cadmium, however, remained essentially unchanged. Concentrations of copper and zinc in the hamster kidney were not affected significantly by subcutaneous administration of copper alone (five daily doses, each of 3.2 mg Cu/kg body wt.), but were increased when gold was given during the copper-treatment. The concentrations of gold, copper and zinc in the renal metallothionein fraction also were increased under these conditions. From these results it seems that kidney metallothionein synthesis in response to gold may be related to the changes in either the concentration or distribution of zinc, rather than copper.     

Metabolism of parenterally administered zinc and cadmium in livers of newborn rats

The interaction of injected zinc and cadmium with metallothionein was investigated in newborn rats. Tissues of 5-day-old rats were removed 24 h after a single injection (Sc) of saline or zinc (20 mg/kg, body wt.) or cadmium (1 mg/kg, body wt.) with 2.5 μCi of ⁶⁵Zn or ¹⁰⁹Cd or 5 μCi of [³⁵S]cysteine. Injection of zinc resulted in a 75% increase in the hepatic zinc concentration with a concomitant elevation of metallothionein (P < 0.001), zinc in metallothionein increased by 45% (P < 0.05); [³⁵S]cysteine incorporation indicated the induced synthesis of metallothionein. Injection of cadmium did not alter either metallothionein or zinc levels in liver, but cadmium in cytosol was preferentially bound to metallothionein. Neither treatment altered hepatic copper metabolism and copper in metallothionein, nor renal zinc and metallothionein levels. These data indicate that zinc injection can elevate hepatic zinc levels and induce metallothionein synthesis in newborn rats despite high basal levels; cadmium injection does not induce metallothionein synthesis, though cadmium is avidly sequestered by pre-existing metallothionein. The differences in the induction of metallothionein by these divalent cations can be explained by the differences in their binding affinities for thiol groups in intracellular metallothionein.     

Effect of 6-mercaptopurine on mineral and metallothionein metabolism in the mouse

The effect of the anticancer drug 6-mercaptopurine (6-MP) on mineral metabolism was investigated in mice. C57Bl/6J female mice were injected intraperitoneally with 6-MP at 100 mg/kg body wt for one, two, four, or five consecutive days. On d 6 of the study, liver, kidney, and intestine were removed, and concentrations of zinc, copper, iron, manganese, magnesium, and calcium were measured. Hepatic concentrations of zinc, copper, iron, and calcium became higher as the number of drug injections increased. To determine if the altered mineral metabolism was a function of a drug-induced, acute-phase response, liver metallothionein and plasma ceruloplasmin were measured. Metallothionein concentrations in the liver became higher with increased number of injections, correlating with the stepwise increase in hepatic zinc. Gel filtration chromatography showed that most of the increase in liver zinc concentration was associated with a protein of mol wt of 6000–8000, the approximate weight of metallothionein. Ceruloplasmin concentrations were not affected by 6-MP injection. These results suggested that 6-MP alters zinc metabolism by sequestering zinc into the liver via induction of metallothionein synthesis and that the drug may induce an acute-phase response with an atypical acute-phase protein profile.     

Zinc availability from zinc lipoate and zinc sulfate in growing rats

The purpose of this study was to investigate the effect of zinc lipoate and zinc sulfate on zinc availability in growing rats. 6 . 6 male albino rats were fed purified diets based on corn starch, egg albumen, sucrose, soy bean oil and cellulose over a 4-week period (diet Ia: 10 mg Zn/kg as zinc sulfate, diet Ib: 10 mg Zn/kg as zinc lipoate, diet IIa: 10 mg Zn/kg as zinc sulfate +0.4% phytic acid, diet IIb: 10 mg Zn/kg as zinc lipoate +0.4% phytic acid, diet IIIa: 20 mg Zn/kg as zinc sulfate + 0.4% phytic acid, diet IIIb: 20 mg Zn/kg as zinc lipoate + 0.4% phytic acid). Zinc lipoate and zinc sulfate both proved to be highly available zinc sources. When 0.4% phytic acid were present in the diets, apparent zinc absorption was generally depressed but was higher from zinc lipoate in tendency than from zinc sulfate. Comparable results were evident for femur zinc, plasma zinc and metallothionein concentrations in liver tissues. This indicates that zinc lipoate could be a valuable zinc source under conditions of low zinc availability. Nevertheless the absence or presence of phytic acid was a more important factor influencing zinc availability than the type of zinc source investigated.     

13-cis-retinoic acid metabolism in vivo. The major tissue metabolites in the rat have the all-trans configuration

The liver and intestinal metabolites of orally dosed 13-cis-[11-3H]retinoic acid were analyzed in normal and 13-cis-retinoic acid treated rats 3 h after administration of the radiolabeled retinoid. all-trans-Retinoic acid was identified as a liver and intestinal mucosa metabolite in normal rats given physiological doses of 13-cis-[3H]retinoic acid. all-trans-Retinoyl glucuronide was identified as the most abundant radiolabeled metabolite in mucosa and a prominent liver metabolite under the same conditions. Thus, the major 13-cis-retinoic acid metabolites retained in liver and mucosa, two retinoid target tissues, had the all-trans configuration. These data indicate that the isomerization of 13-cis-retinoic acid to all-trans-retinoic acid and the subsequent conversion to all-trans-retinoyl glucuronide are central events in the in vivo metabolism of 13-cis-retinoic acid in the rat. Moreover, the all-trans-retinoic acid detected in vivo could account for a significant fraction of the physiological activity of 13-cis-retinoic acid. The tissue disposition and metabolism of orally dosed 13-cis-[3H]retinoic acid are modulated by retinoid treatment. Chronic 13-cis-retinoic acid treatment apparently increased the intestinal accumulation of all-trans-retinoic acid, all-trans-retinoyl glucuronide, and 13-cis-retinoyl glucuronide. The liver concentrations of tritiated all-trans-retinoic acid and all-trans-retinoyl glucuronide were also elevated in 13-cis-retinoic acid treated rats.     

Diabetes and dietary copper alter 67Cu metabolism and oxidant defense in the rat

Perturbations in copper (Cu) metabolism are a characteristic of diabetes, for example, elevated plasma Cu and compromised oxidant defense related to diabetes-induced effects on Cu-containing enzymes. Herein, the redistribution of Cu in selected tissues is described in response to diabetic and nondiabetic states in rats that were fed diets adequate in (12 mg Cu/kg of diet) or deficient in (no added Cu) Cu. Diabetes was induced by intravenous administration of streptozotocin (40 mg/kg body weight). After 5 weeks, rats were gavaged with (67)Cu (0.74 MBq per rat) using the Cu-deficient diet as a vehicle (suspended 1:3 in water) and killed at various time points. The use of (67)Cu allowed for the assessment of short-term Cu distribution and its comparison to the steady-state Cu distribution, as determined by direct Cu analysis. In contrast to control rats, the adaptive mechanisms for Cu homeostasis in diabetic rats were impaired. In general, measures of Cu retention were reduced in diabetic rats compared to corresponding values for control rats. Moreover, diabetic rats had low copper, zinc superoxide dismutase activity that was reduced even further when diabetic rats were fed with low-Cu diets. However, liver and kidney metallothionein and plasma ceruloplasmin levels were elevated in diabetic rats compared to control rats. Such diabetes-related metabolic alterations were taken as measures of increased oxidative stress and inflammation, which may have implications in the progression of diabetes-related pathologies.     

Oral treatment with retinoic acid decreases bone mass in rats

13-cis-retinoic acid (13-cis-RA, isotretinoin) is used to treat severe recalcitrant acne. Other retinoids have adverse effects on bone. Recent studies of human patients treated with 13-cis-RA have had varying results, perhaps because of variability among patients and the lack of control groups. The effects of retinoids have been studied in rodents, but little information is available regarding the effects of clinically relevant retinoid doses as evaluated by use of bone densitometric techniques. We treated rats for 15 or 20 wk with 13-cis-RA, all-trans-RA, or soybean oil (control) by gavage. We used dual-energy X-ray absorptiometry, histomorphometry, and histologic evaluation to evaluate effects on bone. Spontaneous long bone fractures occurred in some rats treated with 15 mg/kg all-trans-RA daily. Bone mineral density, bone mineral content, bone diameter, and cortical thickness of the femur were reduced in rats treated daily with 10 or 15 mg/kg all-trans-RA or 30 mg/kg 13-cis-RA. The lumbar spine was not affected. Although the effects of 13-cis-RA were not as dramatic as those of all-trans-RA, further study of the effects of 13-cis-RA on long bones is warranted.     

Co-administration of zinc and n-acetylcysteine prevents arsenic-induced tissue oxidative stress in male rats

Arsenic is a widespread environmental toxicant that may cause neuropathy, skin lesions, vascular lesions and cancer upon prolonged exposure. Improving nourishment like supplementation of micronutrients, antioxidants, vitamins and amino acids could be able to halve the risk in those who were previously the poor nourished. The present study was planned to investigate the preventive effects of zinc and n-acetylcysteine (NAC) supplementation either alone or in combination with arsenic on selected biochemical variables indicative of oxidative stress and liver injury in male rats. For 3 weeks 25 male wistar rats were exposed to arsenic as sodium arsenite (2 mg/kg, orally through gastric intubation) either alone or in combination with NAC (10 mg/kg, intraperitoneally), zinc (5 mg/kg, orally) or zinc plus NAC. Animals were sacrificed 24h after the last dosing for various biochemical parameters. Concomitant administration of zinc with arsenic showed remarkable protection against blood delta-aminolevulinic acid dehydratase (ALAD) activity as well as providing protection to hepatic biochemical variables indicative of oxidative stress (like thiobarbituric acid reactive substances (TBARS) level, catalase) and tissue injury. NAC supplementation on the other hand, was moderately effective in protecting animals from the toxic effects of arsenic. Interestingly, concomitant administration of zinc and NAC was most effective compared to zinc or NAC in eliciting above-mentioned protective effects. The above results suggest significant protective value of combined zinc and NAC administration in acute arsenic exposure.     

The teratogenic activity of a thalidomide analogus EM12 in rats on a low-zinc diet.

The relationship between the teratogenicity of EM12, 2-(2,6-dioxopiperiden-3'-yl) phthalimidine, a stable analogue of thalidomide, and zinc status in the maternal animal was investigated using pregnant rats on a low-zinc diet (1 ppm zinc, days 0--14 gestation) as the experimental model. Previous studies with this compound in rats fed a commercial diet at oral doses up to 250 mg/kg per day for three days and intravenous doses up to 10 mg/kg per day for three days failed to produce "typical" thalidomide malformations. However, when a dose of 150 mg/kg was given intraperitoneally to rats on a low-zinc diet, typical thalidomide malformations occurred with an incidence of 57.5%.     

Nickel-selenium interaction-time dependent biochemical alterations and metal decorporation in rats

The influence of selenium on the disposition of nickel and on Ni induced metallothionein levels was studied in female rats. Concomitant administration of Se (6.3 mumol/kg, intraperitoneally) and 63Ni (0.12 mmol/kg subcutaneously) lowered the Ni burden of all the soft organs and the plasma ceruloplasmin levels. Selenium caused no potentiating effect on the Ni induced hepatic MT. However, 3 days later, the lowered MT levels appeared related to the corresponding decrease in hepatic Ni content at day 6. The Ni selenide excretable complex and Ni-selenide protein complex appear to be probable mechanisms of the Ni-Se interaction in the present study.     

Effect of low level exposure of lead and cadmium on hepatic estradiol metabolism in female rats

Toxic effect of metal cations on female reproduction and gonadal functions was studied. Adult synchronized female rats were treated intraperitoneally with lead acetate and cadmium acetate separately and in combination (0.025, 0.05 and 0.1 mg/kg body wt) for 15 days. The metabolizing enzymes (17beta-hydroxy steroid oxidoreductase and UDP glucoronyl transferase) activities decreased with increasing dose showing significant change compared to control. Also, significant decrease in cytochrome P450 (CYP450) content was found after the treatment. Displacement of zinc bound to metallothionein was more in cadmium treated rats compared to other groups. In all these parameters, treatment in combination of lead and cadmium showed intermediate results indicating some kind of competition between the two metals. But the histological studies showed that combined treatment caused more cytotoxic effect than cadmium and lead alone. These results indicated that metal cations tested did have a direct inhibitory effect on metabolizing enzyme activities.     

Temporal relationships of the anti-inflammatory effect of etodolac in the adjuvant arthritic rat

Using the curative model of adjuvant arthritis, adult male Sprague-Dawley rats were treated with vehicle or etodolac (1, 3, and 8 mg/kg/day, po) for 9 days. Rats were sacrificed after 1, 2, 4, or 9 daily doses, and paw volume, PGE2 concentrations, and N-acetyl-beta-D-glucosaminidase (NAG) activity were determined in the left adjuvant-injected hindpaws. All three doses of etodolac caused a significant decrease in PGE2 concentrations after the first dose, and the decreases persisted for 2, 4, and 9 days of treatment, respectively. In rats given four daily doses of 3 and 8 mg/kg/day of etodolac, the paw volume was significantly decreased by about 50%, compared with that of the arthritic controls. A significant decrease in NAG activity was observed only after nine daily doses of 8 mg/kg/day etodolac. The sequence of anti-inflammatory events manifested following etodolac treatment would appear to be an initial inhibition of PGE2 synthesis, followed by resorption of fluid, and then by a reduction in macrophage infiltration.