Stimulation of rat liver growth by a single administration of lead nitrate

The effect of a single dose of lead nitrate on hepatic DNA and protein content was investigated in male Wistar rats. Liver enlargement was observed 48 hr after administration of the metal salt. The increase in liver mass was accompanied by an increase in total hepatic DNA and protein content. The enhanced activity of DNA synthesis was also shown by a significant increase in the incorporation of [³H]thymidine into DNA of animals treated with lead nitrate thus suggesting that the observed hepatomegaly could be a consequence of lead nitrate-induced hepatic hyperplasia rather than cellular hypertrophy.     

Effects of S-8527 (1,1-bis(4'-(1'-carboxy-1'-methylpropoxy)phenyl) cyclohexane), a new hypolipidemic compound, on cholesterol and lipoprotein metabolism in rats.

The effects of S-8527 (1,1-bis[4'-(1Prime;-carboxy-1Prime;-methylpropoxy)phenyl]cyclohexane on cholesterol and lipoprotein metabolism were examined and compared with those of clofibrate in rats under various experimental conditions. When rats were given a daily oral dose of S-8527 for 8 days, the incorporation of [¹⁴C]acetate into liver cholesterol was not inhibited at the dose of 30 mg/kg of S-8527. which was reported to decrease the serum cholesterol significantly, but the higher dose (300 mg/kg) of S-8527 decreased the incorporation of [¹⁴C]acetate into liver cholesterol. Under these experimental conditions, clofibrate (300 mg/kg) caused a decrease in labeled cholesterol in the liver. Oral doses of S-8527 or clofibrate for 8 days did not affect the incorporation of [¹⁴C]mevalonate into liver cholesterol. Also, when the drugs were added to normal rat liver slices, the effects of S-8527 were not so marked as those seen with clofibrate. Oral doses of S-8527 (30 mg/kg) or clofibrate (300 mg/kg) for 8 days decreased the incorporation of [¹⁴C]lcucine into the protein of serum lipoproteins. S-8527 and clofibrate did not affect the body retention of radioactivity after the injection of labeled cholesterol into rats. In view of the above results, it is conceivable that S-8527 primarily inhibits either the secretion of lipoproteins containing cholesterol into plasma or the formation of lipoproteins containing cholesterol in the liver, or both, and secondarily interferes with the biosynthesis of liver cholesterol.     

Effect of slow and rapid cystometry on in vitro rat urinary bladder DNA synthesis

1. Partial outflow obstruction induces marked changes in detrusor contractile function and morphology. One common finding in all experimental animal models of partial outflow obstruction is a significant increase in bladder mass.2. Previous studies have demonstrated that partial outlet obstruction induces a rapid and substantial increase in [³H]thymidine incorporation into virtually all cellular elements of the bladder.3. The present study was designed to investigate the [³H]thymidine uptake and localization induced by exposure of the in vitro whole rat bladder model to various intravesical pressures and rates of intravesical infusion.4. The results are as follows:(a) There were no differences in DNA concentration between control and other groups.(b) Slow infusion induced a mild increase in DNA synthesis ([³Hthymidine incorporation) at 0.5 ml and a significantly greater level of DNA synthesis at 1.6 ml.(c) [³H]thymidine incorporation was significantly increased by exposure to 7.5 cm H₂O, 15 cm H₂O, and 30 cm H₂O.(d) Exposure to 60 cm H₂O and 90 cm H₂O did not initiate an increase in [³H]thymidine incorporation.(e) Autoradiography showed that all tissue elements (urothelium, connective tissue, smooth muscle) participated in the response.     

Effects of drug metabolism inhibitors on butylated hydroxytoluene-induced pulmonary toxicity in mice

The administration of butylated hydroxytoluene (BHT) to mice results in lung cell damage followed by cellular proliferation which was quantitated by measuring the increase in thymidine incorporation into pulmonary DNA. Administration of SKF 525-A or piperonyl butoxide to mice treated with BHT prevented the increase in thymidine incorporation into pulmonary DNA. This effect was dose dependent, with complete protection from 400 mg/kg BHT achieved with 10 mg/kg SKF 525-A or 400 mg/kg piperonyl butoxide. SKF 525-A and piperonyl butoxide completely prevented the BHT-induced increase in pulmonary DNA synthesis even when given 1–2 hr after BHT and a partial protective effect was evident when they were given 6–12 hr after BHT. Pretreatment of mice with cobaltous chloride diminished the BHT-induced increase in thymidine incorporation into pulmonary DNA. Following the in vivo administration of [¹⁴C]BHT, radioactivity was covalently bound to lung, liver, and kidney macromolecules of both mice, which exhibited BHT-induced lung damage, and rats, which did not. The greatest amount of radioactivity was bound to lung tissue from mice. This binding was prevented by the administration of SKF 525-A and was a linear function of the BHT dose within a range of 50–600 mg/kg. Binding to other tissues from the mouse and all tissues examined in the rat was minimal and unaffected by SKF 525-A. These data suggest that a reactive metabolite of BHT rather than the parent compound produces lung damage in mice.     

Lymphoid suppression by cis-platinum(II)amines: What are the active agents?

Cisplatin and its various hydrolysis products were tested in vitro for their effects on the incorporation of [³H]thymidine into lymphocytes isolated from thymuses, spleens and stimulated lymph nodes of rats. Neither cisplatin nor the μ-hydroxo-bridged oligomers formed after hydrolysis significantly inhibited thymidine incorporation at pH7.4. However, freshly neutralised cis-diaquodiammineplatinum(II) was a potent inhibitor of thymidine incorporation by all three lymphocyte populations.In other experiments, rats were given either cisplatin or one of its hydrolysis products i.p. Cells isolated 17 hr later from the thymuses of all of these animals incorporated much less [³H]thymidine into DNA in vitro than thymocytes from saline-injected control animals. None of the platinum species significantly affected either [³H]uridine incorporation or the oxidation of [¹⁴C]octanoate to ¹⁴CO₂ by the thymocytes.Evidence for anation of di- and tri-nuclear μ-hydroxo-bridged platinum(II)amines by chloride has been obtained from spectrophotometric analyses and ¹⁹⁵Pt-NMR studies. Thiols also reacted with these platinum complexes at different rates (cis-[(NH₃)2Pt(H₂O₂)]²⁺ > derived oligomers > cisplatin).Various mechanisms for lymphoid suppression by cisplatin and its hydrolysis products are considered. It is proposed that cisplatin and its μ-hydroxo-bridged derivatives owe their lymphotoxic activity primarily to their in vivo transformation to platinum species containing aquo ligands.     

Disposition of clofibrate in the rat: Acute and chronic administration

The disposition of 1-[¹⁴C]clofibrate (0.4 $\text{mmole}\text{kg}$) was studied in rats after acute (single dose) and chronic (b.i.d., for 14 days) administration. With a single dose (orally or by intraperitoneal injection) of clofibrate, most (~90 per cent) of the ¹⁴C-dose appeared in the urine within 24 hr and the recovery of ¹⁴C from the urine and feces was nearly quantitative within 72 hr. Little fecal excretion of ¹⁴C (< 5 per cent) occurred after a single or chronic clofibrate administration. Clofibrate was readily absorbed and eliminated, as evidenced by a rapid increase in plasma ¹⁴C level within 90 min and a calculated biological half-life of 4.1 hr. The pharmacokinetic profile of ¹⁴C-elimination in rats was unaffected by pretreatment with cholestyramine. Clofibric acid [2-(4-chlorophenoxy)-2-methylpropionic acid] was identified as the major metabolite in plasma (~97 per cent) whereas the glucuronide of clofibric acid was the main urinary and biliary metabolite (~96 per cent). Clofibric acid, as the free acid and glucuronide form, accounted for 99 per cent of the total ¹⁴C-dose in rats, and unchanged clofibrate was not detected in any of the biological samples. Two unidentified, minor urinary metabolites were also detected. In cannulated bile duct studies, it was found that [¹⁴C]clofibrate, as clofibric acid, was rapidly and efficiently excreted in the bile. The biliary excretion rates of ¹⁴C and of the glucuronide of clofibric acid were also not altered by phenobarbital pretreatment. Chronic treatment with [¹⁴C]clofibrate did not alter the qualitative or quantitative nature of biotransformation in vivo. An increased rate of urinary ¹⁴C-elimination was observed following chronic 1-[¹⁴C]clofibrate treatment, with concomitant reductions in blood and heart ¹⁴C-content and an elevation in ¹⁴C-content of epididymal fat tissue. Subcellular fractionation of liver, from rats given [¹⁴C]clofibrate chronically, indicated an increased distribution of ¹⁴C into mitochondria and peroxisomes. Tissue ¹⁴C-levels, achieved in these in vivo studies, were an order of magnitude lower than those required for the pharmacological activities of clofibrate and clofibric acid in vitro.     

Enhanced liver DNA synthesis in partially hepatectomized rats pretreated with 2,3,7,8-tetrachlorodibenzo-p-dioxin

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on liver DNA synthesis was studied in rats after a $\text{1}\text{3}$ hepatectomy. The rats were maintained on a controlled feeding schedule and were treated with 5 μg/kg of TCDD or acetone/corn oil (control). Five days after treatment a $\text{1}\text{3}$ hepatectomy was performed and at designated times thereafter liver DNA synthesis was measured by [³H]thymidine incorporation into DNA. The main finding was that liver DNA synthesis was increased 8- to 10-fold by TCDD over that which was observed in control rats. This increase occurred after a latency period that was appropriate for the regenerative liver DNA synthesis response. Other experiments showed that increased incorporation of thymidine in TCDD-treated rats could be blocked by hydroxyurea, an inhibitor of semiconservative DNA synthesis, and that the increased incorporation was secondary to increased DNA synthesis and not increased thymidine kinase activity. Thus, hepatocytes in TCDD-treated rats respond in a quantitatively different manner than control rats to the same proliferative signal, $\text{1}\text{3}$ hepatectomy. Liver DNA synthesis in nonhepatectomized TCDD-treated rats tended to be greater than control, but the difference was not statistically significant.     

A comparison of mirex-induced liver growth to liver regeneration

In intact rats given a single oral dose of mirex there was a dose-dependent increase in liver weight which peaked at 4 days. There were increases in hepatic RNA and protein, but DNA content per liver and DNA synthesis as measured by [3H]thymidine incorporation were unchanged. In partially hepatectomized rats dosed with mirex 24 h post-surgery, there was a dose-dependent increase in relative liver weight which peaked at 5 days. In partially hepatectomized rats simultaneously dosed with mirex, [3H]thymidine incorporation into DNA was unaltered. However, in rats dosed with mirex 24 h prior to partial hepatectomy, there was a 50% reduction in [3H]thymidine incorporation into hepatic DNA.     

The effects of chlorambucil on the utilization of exogenous thymidine by tumour cells.

Treatment of an alkylating agent-sensitive strain of the Yoshida ascites sarcoma with chlorambucil resulted in an inhibition of the incorporation of [³H]thymidine into DNA, which could be overcome by incubating cells in high extracellular concentrations of thymidine. Increase in cellular DNA content and the dilution of specific radioactivity in pre-labelled DNA indicated that DNA synthesis was continuing at times when [³H]thymidine incorporation was inhibited. Uptake and phosphorylation of thymidine were not impaired by the treatment and the reduced incorporation of [³H]thymidine into DNA is attributable to a block in the utilization of TTP derived from exogenous nucleoside.     

Effect of 3,7-bis-(4-trifluoromethylphenyl)-1,5,3,7-dioxadiazocane on pyrimidine and DNA synthesis in rat organs

The administration of the lipophilic 3,7-bis-(4-trifluoromethylphenyl)- 1,5,3,7-dioxadiazocane (TFMPD) to rats induced the following effects on the biosynthesis of DNA in the liver, kidney, thymus and spleen: (a) The utilization of [3H]thymidine for the synthesis of liver DNA thymine was decreased after the administration of a single dose of the drug. The depression of the specific activities of DNA pyrimidines of liver DNA in experimental groups was observed also after an injection of [14C]orotic acid. (b) A decreased incorporation of labeled thymidine had occurred also in the spleen during the prereplicative period. Thereafter the specific activity of DNA thymine was higher than in the control group. (c) The observed mitogenic response in the spleen showed a protracted effect; after the administration of a single dose of the drug the specific activity of DNA thymine as well as the thymidine kinase activity of spleen cytosol have been rising up to the ninth day. The same holds true for DNA thymine of the thymus; the activity of thymidine kinase was not affected. (d) Both the single and repeated doses of TFMPD had no marked effect on the levels of microsomal cytochromes P-450 and b5 in the liver and kidney.     

醋酸棉酚对肝脏、睾丸和小肠等组织H3-胸腺嘧啶核苷参入的影响

In order to elucidate the mode of action and toxic effect of gossypol, its effects on the incorporation of H³-thymidine (H³-TdR) into DNA of the regenerative liver, testis and small intestine of adult male rats, the liver, small intestine and thymus of preadult male rats and the liver and small intestine of adult male mice have been studied. An antimetabolite-5Fu was studied in the experiments for comparison. The results showed that 5Fu inhibited significantly the incorporation of H³-TdR into DNA of the thymus, small intestine and liver of "regenerative liver" but there was no significant change in the tissues of the gossypol-treated animals, which seemed to indicate a lack of effect of gossypol on the synthesis of DNA. However, when the dosage of gossypol was increased so that atrophy of the testis appeared, the incorporation of H³-TdR and the specific activity of DNA in the testis was higher in the experimental than in the untreated control animals. A discussion of these results was given.     

Comparison of the subacute effects of cadmium exposure upon nucleic acid, cyclic adenosine 3',5'-monophosphate and polyamine metabolism in lung and kidney cortex.

The timecourse of the cadmium-inflicted changes in DNA, polyamines, and cyclic AMP has been investigated in lung and renal cortex tissue of rats. In pulmonary tissue, heavy metal administration (2 × 1.0 mg/kg/day) produced an initial depression in the incorporation of [¹⁴C]-thymidine into DNA after 3 days, followed by a subsequent, significant enhancement at 5 days with maximal augmentation occurring after 7 days of cadmium treatment. In contrast the incorporation of labeled thymidine into kidney cortex DNA was decreased at all time periods studied and statistically significant reduction to at least half of the control values was noted at 3, 5 and 7 days. No apparent differences were found between pulmonary and renal DNA concentrations which were decreased at 1 day and elevated after 7 days of cadmium exposure in both tissues. Whereas cadmium significantly lowered lung RNA concentrations after 1, 3, or 5 days, heavy metal treatment failed to produce any significant change in RNA content of the kidney cortex. In general, subacute exposure to cadmium resulted in a significant rise in pulmonary putrescine, spermidine, and spermine after 3 and 5 days, although a significant depression was observed at 7 days in the case of putrescine. Surprisingly, the renal concentrations of putrescine and spermine were elevated in metal-treated animals but there was a statistically significant reduction in spermidine content. As in the case of incorporation of [¹⁴C]-thymidine into DNA, pulmonary cyclic AMP concentrations were depressed initially at 1 day and continuation of cadmium treatment for 3, 5, or 7 days resulted in enhancement of cyclic nucleotide concentration. In contrast, administration of the heavy metal lowered both the incorporation of thymidine into DNA and the concentration of cyclic AMP in renal cortex at all time points examined. The data demonstrate that even though the responsiveness of lung to subacute cadmium exposure differs from that of kidney cortex, the observed alterations in DNA synthesis may be mediated through modulation of cyclic AMP (and possibly polyamine levels) in both tissues.     

A comparison of the effects of paraquat and diquat on the water content of rat lung and the incorporation of thymidine into lung DNA

Following the administration to rats of approximately equitoxic doses of paraquat and diquat by intraperitoneal injection, the pattern of mortality was different. After dosing with paraquat, there were no deaths in the first 24 h, whereas 22% of the rats given diquat died in this period. The largest proportion (34%) of the rats which died following paraquat administration, did so on the third day after dosing. The death of paraquat-poisoned rats has been shown to be related to lung damage as measured by a greatly increased water content. There was no similar increase in the water content of lungs taken from rats poisoned with diquat. Thymidine incorporation into lung DNA was significantly decreased one day after dosing with both paraquat and diquat, but became greatly elevated in a proportion of those rats given paraquat which survived 3 days after dosing. In diquat-poisoned rats, thymidine incorporation into lung DNA remained depressed for at lease 8 days.It is concluded that: (1) most rats given paraquat by intraperitoneal injection die from acute lung damage characterised by a dramatic increase in the lung water content; (2) only a small proportion die many days later from lung fibrosis characterised by an increase in thymidine incorporation into DNA; and (3) diquat does not cause lung damage as characterised by increases in either the water content of lung or increases in thymidine incorporation into DNA.     

A subcellular study of the clofibratei-nduced increase in coenzyme a concentration in rat liver

When clofibrate [ethyl 2-(4-chlorophenoxv)-2-methylpropionatel was administered subcutaneously to rats (600 $\text{mg}\text{kg}$ per day for 3 days), the concentration of CoA and its acyl derivatives in the liver increased 2.5-fold. Forty-eight per cent of the total cellular CoA in the clofibrate-treated rat liver and 51 per cent in the control liver was found in the mitochondrial fraction. In order to study the intermediates of CoA synthesis, clofibrate-treated rats were injected with [³H]pantothenate intracardially and killed after 30 min, l or 2hr for determination of the incorporation of radioactivity into CoA and its precursors. The incorporation of pantothenate into CoA after 2 hr was 5.9-fold in the liver and 4.5-fold in the liver mitochondrial fraction as compared with the control values. Measurement of the pantothenate concentration and radioactivity in clofibrate-treated and control rat liver showed that the higher incorporation of [³H]pantothenate into CoA in clofibrate-treated rat liver cannot be the result of a higher specific radioactivity of pantothenate. It is therefore evident that clofibrate affects the CoA concentration by increasing the rate of synthesis, although the rate of CoA degradation is simultaneously decreased, as has been shown previously [9]. The present results indicate that clofibrate increases the total hepatic CoA concentration without affecting the intracellular compartmentation of CoA. The clofibrate-induced increase in the rate of CoA synthesis does not result in differences in the compartmentation of the intermediates of CoA synthesis.     

The effect of external deoxyribonucleosides on deoxyribonucleoside triphosphate concentrations in human lymphocytes.

The effects of deoxyribonucleosides on the intracellular levels of deoxyribonucleoside triphosphates (dNTP) and on the rate of labelled thymidine incorporated into DNA of human phytohaemag-glutinin-stimulated lymphocytes have been studied. Thymidine (10^?2–10^?6M) expanded the dTTP and reduced dATP and dCTP levels. Deoxycytidine (10^?3M) expanded the dCTP level and caused inhibition of [³H] thymidine incorporation into DNA but had no detectable effect on the other dNTP concentrations. Deoxyadenosine (10^?3 M) expanded the dATP level, and reduced the other dNTP levels and deoxyguanosine (10^?4M) expanded the dGTP level and reduced the dCTP level; both inhibited [³H] thymidine incorporation into DNA. The sensitivity of these cells to the addition of deoxynucleosides to their culture medium indicates that the plasma and tissue levels of nucleosides may profoundly influence DNA synthesis by human cells in vivo.     

In vivo inhibition of hepatic lipogenesis in the rat by cyclandelate (3, 3′, 5-trimethylcyclohexanylmandelate)

Rates of hepatic lipogenesis were measured in vivo in rats by incorporation into lipids of [³H] from injected [³H]H₂O 17 hr after a single oral dose of cyclandelate (3, 3′,5-trimethylcyclohexanylmandelate, a vasoactive substance). Cyclandelate administration resulted in a significant inhibition (40–60%) of both sterol and fatty acid synthesis in the livers which was independent of the 3.2-fold diurnal variation in the rates of hepatic sterol and fatty acid synthesis. The inhibition of accumulation of newly synthesized fatty acid in intestine also reached statistical significance. The accumulation of newly synthesized sterol was significantly depressed in serum but did not result in any change in the concentration of serum total cholesterol. These results are interpreted in terms of the inhibitory effect of cyclandelate on hepatic 3-hydroxy-3-methylglutaryl-CoA reductase previously reported by us (Biochem. Pharmac. 32, 649, 1983).     

Rebound of rat carrageenin granuloma following cessation of anti-inflammatory steroid therapy

Glucocorticoid therapy induced rapid involution of chronic granulomatous inflammation in rats by subcutaneous injection of carrageenin. Hydrocortisone acetate injected into the granuloma pouch at doses higher than 3 mg/kg/day for 3 days caused maximum involution. After withdrawal of the corticoid therapy, rebound of the granulomatous inflammation took place resulting in rapid recovery of the wet weight and total content of tissue DNA and non-collagen proteins. A dose of 3 mg/kg/day was optimal for observing this rebound phenomenon. In order to investigate metabolic aspects of the rebound phenomenon minced granuloma was incubated in vitro with [³H] thymidine or [³H] proline. The rate of incorporation of the labeled precursor into non-collagen protein was elevated near to the normal level by 24 hr after the interruption of the corticoid treatment. A second step in the course of the recovery was a rapid increase in the incorporation of labeled thymidine into DNA which was attained by 48 hr after the last injection of the corticoid. The rate of recovery of the total amount of non-collagen protein, however, was rather slow compared with that of DNA which reached the control level 3 days after the withdrawal of the corticoid therapy. The total non-collagen protein of the granuloma reached almost complete recovery 1 day later. These results suggest that the synthesis of some fractions of the granuloma proteins which involve proteins essential for DNA synthesis was activated before the reactivation of the synthesis of DNA and some other proteins. Recovery of collagen synthesis was not complete until 4 days after the cessation of the corticoid treatment. Consequently, the total amount of collagen was still lower than that of the control on the last day of the experiment.     

氯苯丁酯引起大鼠肝肿大与肝细胞生长因子产生的可能关系

目的研究氯苯丁酯引起的大鼠肝脏肿大与血浆中ＨＧＦ水平变化的关系。方法氯苯丁酯（５００，４００，３００，１００ｍｇ·ｋｇ－１·ｄ－１）加入饲料中喂养大鼠，在不同时间处死大鼠，取出肝脏称重和制备血清，以原代培养大鼠肝细胞ＤＮＡ合成检测ＨＧＦ的生物学活性。结果氯苯丁酯处理后的大鼠血清能显著增加原代培养大鼠肝细胞３Ｈ－ＴｄＲ的参入，ｃｐｍ值随着血清被稀释而逐渐降低，但仍高于对照组。大鼠血清中ＨＧＦ的释放在给药后４ｄ达到最高水平，为正常对照组的６倍以上，给药２ｗｋ后仍维持在正常水平的２倍以上。而氯苯丁酯引起肝脏肿大发生在给药２ｗｋ后，并维持在正常水平的１．８倍以上。结论氯苯丁酯引起的肝脏肿大可能部分与ＨＧＦ促肝细胞的增殖作用有关     

Alterations in [3H]thymidine incorporation into DNA and [3H]uridine incorporation into RNA induced by 5-azacytidine in vivo.

Administration in vivo of 5-azacytidine (5-aza-CR) caused suppression of [³H]thymidine ([³H]TdR) incorporation into DNA of bone marrow and gastrointestinal mucosa of mice and a more prolonged suppression of L1210 ascites tumor. Single doses of 5-aza-CR caused a modest and short-lived suppression of incorporation of [³H]uridine ([³H]UR) into nuclear RNA of L1210 ascites tumor cells. No suppression of [³H]UR incorporation into RNA of bone marrow or gastrointestinal mucosa was observed. L1210 tumor cells resistant to the other active cytidine analogue, cytosine arabinoside, demonstrated less disruption of [³H]TdR incorporation after exposure to 5-aza-CR, suggesting some cross resistance in the effects of these two drugs on DNA synthesis. Survival studies carried out in mice bearing both the sensitive and resistant L1210 tumor cell lines confirmed cross resistance of the anti-tumor effects of the two cytidine analogues. Second doses of 5-aza-CR, with the timing og administration based upon the differing patterns of recovery of [³H]TdR incorporation between normal tissues and tumor cells, led to a prolongation of survival in mice bearing the sensitive L1210 ascites tumor.     

Repair of rat liver DNA in vivo damaged by ethylene dibromide.

Tube feeding of [¹⁴C]Jethylene dibromide (EDB) to non-fasted rats resulted in the incorporation of the radioactivity into liver DNA, RNA and protein. Using alkaline and neutral sucrose gradients, it was observed that administration of the pesticide to non-fasted rat caused slower sedimentation of liver DNA in alkaline and not in neutral sucrose gradients. Slower sedimentation of liver DNA in alkaline sucrose gradients was apparent within 2 hr after the administration of a dose of 22 mg/100 g or 4 hr after a dose of 7.5 mg/100 g of body weight. Using a dose of 7.5 mg/100 g, the EDB-induced liver DNA damage was repaired significantly by 17.5 hr and almost completely by 96 hr. Administration of diethyldithiocarbamate, a free radical scavenger, did not inhibit liver DNA damage caused by EDB.