Effects of butyltin compounds on mitochondrial respiration and its relation to hepatotoxicity in mice and Guinea pigs.

Because the mechanisms responsible for the difference in toxicity between different experimental animal species remain unclear, the effects of tributyltin chloride (TBTC) and dibutyltin dichloride (DBTC) on mitochondrial respiration were compared among the livers of mice and guinea pigs in vitro and in vivo. Further, the levels of these butyltin compounds and their derivatives in the mitochondrial fractions of the hepatocytes were investigated in these animal species. Administration of TBTC and DBTC to mice resulted in the obvious elevation of serum enzymatic activities, as well as the inhibition of succinate-linked State 3 respiration in hepatic mitochondria at 24 h after administration. On the other hand, these metal compounds failed to induce such hepatotoxicity or to inhibit mitochondrial respiration in guinea pigs. There was no significant difference between mice and guinea pigs in the IC50 (metal concentration observed in 50% inhibition of mitochondrial respiration) of TBTC and DBTC against the succinate-linked State 3 respiration of hepatic mitochondria in vitro, although the mitochondrial respiration of succinate-linked State 3 was inhibited in the liver of mice treated with the metals in vivo. The levels of total butyltin compounds in the mitochondrial fractions of hepatocytes were higher in the mice than in the guinea pigs, and the main butyltin compound in the mitochondrial fractions was DBTC in both species at 24 h after TBTC or DBTC administration. The amount of sulfhydryl groups, which were capable of binding with DBTC, in mice hepatic mitochondria was twice as large as that in guinea pigs, and the affinity of DBTC for the isolated hepatic mitochondria was higher in mice than in guinea pigs in vitro. These results suggested that the induction of hepatotoxicity by TBTC and DBTC in vivo was closely associated with the depression of mitochondrial respiration and that the difference in susceptibility to the metal-induced mitochondrial damages between mice and guinea pigs might result from the high affinity of butyltin compounds, in particular DBTC, for hepatic mitochondria in mice containing higher levels of sulfhydryl groups, compared with guinea pigs.     

Histamine catabolism in guinea pigs, rats and mice

Histamine catabolism in vivo was studied in unanesthetized rats and guinea pigs; tissues from animals sacrificed 10 min after s.c. injection of ¹⁴C-histamine were assayed for ¹⁴C-histamine and total ¹⁴C. Groups pretreated with aminoguanidine, a diamine oxidase inhibitor, and methylhistamine, an inhibitor of the histamine-methylating enzyme, were used to evaluate roles of these enzymes in individual tissues. For rats the data suggested presence of both enzymes in intestine, diamine oxidase in lung and liver, methylation in kidney, and marked ability of heart to extract ¹⁴C-histamine from blood; these results closely check earlier data from tissues of anesthetized rats sacrificed 2.5 min after i.v. injection of ¹⁴C-histamine. For guinea pigs intestine showed evidence for both enzymes, liver and kidney for diamine oxidase, and lung and heart, for methylation. Since in animals injected with ¹⁴C-histamine, aminoguanidine pretreatment sharply reduced total ¹⁴C in mouse intestine and rat liver, another diamine oxidase inhibitor was tested; similar results were obtained. Amodiaquine, a strong inhibitor of histamine methylation in vitro, was found to inhibit in vivo. Catabolism of endogenously formed ¹⁴C-histamine was tested in the female rat, an animal which destroys exogenous histamine largely through the diamine oxidase pathway. Rats pretreated with aminoguanidine and then injected with ¹⁴C-L-histidine, excreted only slightly more ¹⁴C-histamine in urine than did controls. The ineffectiveness of aminoguanidine suggests that even in the female rat, diamine oxidase may have little significance in local catabolism of newly formed histamine. Possible reasons are discussed.     

Effects of dehydroepiandrosterone on oleic acid formation in the liver of rats, mice and guinea pigs

The purpose of the present study is to answer the question of whether there is a species difference in the effects of a pharmacological dose of dehydroepiandrosterone (DHEA) on the enzymes that participate in oleic acid (18:1) formation in the liver. Feeding a diet containing 0.5% (w/w) DHEA for 14 days markedly increased the activities of acyl-coenzyme A (CoA) synthetase, palmitoyl-CoA chain elongase and stearoyl-CoA desaturase in the liver of rats and mice. These enzyme activities, however, were not changed by DHEA in guinea pigs. The treatments of rats and mice with DHEA markedly increased proportions of 18:1 in hepatic lipids, especially phosphatidylcholine (selectively at C-2 position), triacylglycerol and cholesterol ester. DHEA caused no significant changes in acyl compositions of hepatic lipids of guinea pigs. The levels of DHEA or dehydroepiandrosterone sulfate (DHEAS) were markedly increased in serum and livers by DHEA administration to rats, mice and guinea pigs. High correlations were observed between hepatic levels of DHEA or DHEAS and stearoyl-CoA desaturase activities in rats. These results indicate that there are species differences in the inducing effects of DHEA or DHEAS on hepatic formation of 18:1 and that guinea pigs lack the machinery to induce the enzymes.     

Comparative hepatotoxicity and metabolism of N-methylformamide in rats and mice

N-methylformamide (NMF) produced dose-dependent zone 3 haemorrhagic necrosis in mice; the threshold dose was 100–200 mg/kg. In rats a dose of 1000 mg/kg caused hepatic damage in some animals and slight elevations of plasma transaminases. A species difference in susceptibility to NMF-induced hepatotoxicity is clearly indicated. NMF depleted liver non-protein sulphydryl (NPSH) in a dose-dependent manner in mice, but not in rats. Depletion of liver glutathione by buthionine sulphoximine or diethylmaleate potentiated the hepatotoxicity of NMF in mice. [¹⁴C]-methyl NMF was metabolised by mice and rats and a number of urinary metabolites including an N-acetylcysteine conjugate, methylamine and N-hydroxymethylformamide were detected. There were no qualitative differences in the metabolites between rats and mice but mice metabolised NMF much faster and more extensively than rats.     

Effect of SKF-525A on liver metabolism and hepatotoxicity of tri- and dibutyltin compounds in mice

The effect of pretreatment with SKF-525A, which inhibits hepatic cytochrome P450 enzymes, on metabolism and hepatotoxicity was examined in mice orally administered tributyltin chloride (TBTC) or dibutyltin dichloride (DBTC) at a dose of 180 μmol/kg. Analysis of butyltin compounds showed that the main metabolites in liver of mice treated with TBTC alone were DBTC (40%) and dibutyl(3-carboxylpropyl)tin chloride (TCOOH; 12–26%), with the levels of other butyltin compounds including TBTC comprising <12% of total butyltin compounds at 3–24 h following treatment. The pretreatment with SKF-525A resulted in four- to tenfold increased TBTC levels and a significant decrease of debutylated metabolites, particularly DBTC (60 and 37% decrease) at both 3 and 6 h in liver of mice treated with TBTC, leading to complete inhibition of hepatotoxicity at 24 h. At 24 h after TBTC treatment, hepatic levels of TBTC and most of the debutylated metabolites in mice pretreated with SKF-525A did not differ significantly when compared to those in unpretreated mice, resulting in the induction of hepatotoxicity at 48 h, although levels of TCOOH decreased even at 24 h. In the case of DBTC treatment, >95% of the butyltin compounds were detected as DBTC in liver, and the levels of DBTC inside cells as well as the induction of DBTC hepatotoxicity were unaffected by pretreatment with SKF-525A. These results suggest that debutylated metabolites, in particular DBTC, are the main metabolites of butyltin compounds responsible for the induction of hepatotoxicity following in vivo administration of TBTC. The results also indicate that cytochrome P450 enzymes may play a greater role in the metabolism of TBTC to form DBTC or butyltin trichloride (MBTC) than that of DBTC to form MBTC in liver of mice. Received: 22 October 1996 / Accepted: 24 February 1997     

Comparison of hepatotoxicity caused by mono-, di- and tributyltin compounds in mice

 The in vivo induction of hepatotoxicity, as evaluated by the activity of ornithine carbamyl transferase in serum, was investigated in mice administered orally with the following three butyltin compounds: tributyltin chloride (TBTC), dibutyltin dichloride (DBTC) and monobutyltin trichloride (MBTC). The minimal concentrations of TBTC and DBTC that caused hepatotoxicity at 24 h after oral administration were 180 μmol and 60 μmol/kg, respectively, while MBTC did not induce liver injury even at 7000 μmol/kg. Additionally, when the administered doses were equivalent (180 μmol/kg), a time course (3–96 h) study revealed that the hepatotoxicity of TBTC and DBTC appeared at 24 and 12 h, respectively, but that MBTC showed no hepatotoxicity even at 96 h. The amounts of Sn excreted into urine for 4 days were 1.5 fold greater with TBTC than with DBTC treatment and were lowest in MBTC group. Similarly, the total liver Sn content was 2- to 5-fold greater in the TBTC group than in the DBTC group whereas the liver Sn content in the MBTC treatment showed the lowest value throughout the 3- to 96-h period. Thus, the non-hepatotoxicity of MBTC may be due either to low absorption through the digestive tract of mice or to the low levels of Sn in liver; however, the level of Sn in liver was not associated with the induction of hepatotoxicity by TBTC and DBTC. The analysis of metabolites of TBTC (180 μmol/kg) and DBTC (60 μmol/kg) at equivalent hepatotoxicity showed that the main tin compounds in the liver after the administration of TBTC were dibutyltin and monobutyltin as well as inorganic tin compounds, while most (>78%) of the total tin compounds in the liver of mice treated with DBTC was in the form of dibutyltin. In addition, the levels of monobutyltin and inorganic tin compounds in the livers of mice treated with TBTC were greater than those with DBTC, but the levels of dibutyltin did not differ significantly between TBTC and DBTC. The levels of lipid peroxidation (LPO) and hepatic glutathione (GSH) content in the liver showed a transitory increase after the administration of MBTC and TBTC, respectively. These results suggest that DBTC is more hepatotoxic than TBTC, and that dibutyltin inside the cells may be the main form of tin which is responsible for induction of hepatotoxicity following in vivo administration of TBTC and DBTC. The generation of free radical species, as evaluated by LPO and GSH levels, may not be associated with the hepatotoxicity caused by butyltin compounds. Received: 13 April 1994 / Accepted: 25 May 1994     

Toxicity and metabolism of a new insect repellent N,N-diethylphenylacetamide in mice, rats and guinea pigs on cutaneous application

Cutaneous LD50 of N,N-diethylphenylacetamide (DEPA), a new multi insect repellent was 2200, 3200 and 7100 mg/kg body weight in female mice, rats and guinea pigs; and 1600 and 4000 mg/kg in male mice and rats indicating a high degree of safety on skin contact. Dermal application of DEPA to young growing rats for 21 days at a dose of 50 mg/kg did not exert any adverse effects while massive doses of 500 and 1000 mg/kg caused marked reduction of body weight gain and lowering of activities of serum alanine aminotransferase, aspartate aminotransferase and cholinesterase. Along with DEPA, N-ethylphenylacetamide, phenylacetamide and phenylacetic acid were detected in the urine of DEPA treated mice, rats and guinea pigs.     

Comparative studies on the anorectic activity of d-fenfluramine in mice,rats, and guinea pigs

Summary The present study compares the anorectic activity of d-fenfluramine and its metabolite d-norfenfluramine in three animal species. d-Fenfluramine and d-norfenfluramine show anorectic activity at increasing doses (ED₅₀) in rats, guinea pigs, and mice, d-norfenfluramine being more active than d-fenfluramine in all three species. Equiactive anorectic activities are reached with different brain levels of d-fenfluramine and d-norfenfluramine, guinea pigs being the most sensitive species, followed by rats then mice. The metabolite most probably plays a major role in the anorectic effect of d-fenfluramine in guinea pigs, contributes to the anorectic activity in rats, but adds little to the action of the parent drug in mice. The different sensitivity to d-fenfluramine and d-norfenfluramine in these three species does not appear to be explained by a number of biochemical parameters, including serotonin uptake or release, receptor subtypes, or ³H-d-fenfluramine binding and uptake. Send of fprint requests to T. Mennini at the above address     

Benzonal metabolism in guinea pigs

A metabolite of an anticonvulsant drug Benzonal was isolated from the guinea pig blood serum and identified by high performance liquid chromatography (HPLC). By using HPLC as well as ultraviolet-, infrared- and mass-spectrometry it was established that in the guinea pig intestine Benzonal undergoes alkaline hydrolysis with the formation of phenobarbital. The native Benzonal in the guinea pig blood serum was not found.     

Percutaneous absorption of hexachlorophene in rats, guinea pigs and pigs

A comparative study of the percutaneous absorption of hexachlorophene (HCP) was undertaken in rats, guinea pigs and pigs. [14C]Hexachlorophene ([14C]HCP) was applied evenly over the shaved back of the animals at a dose of 40 microgram/cm2 skin surface. Urine and feces were collected at 24-h intervals for 5 days from animals kept in metabolism cages. Different methods were used for quantitating the percutaneous absorption of HCP. This study showed that skin permeability to HCP decreased in the following order: rat, guinea pig and pig. The permeability characteristics of the pig skin to topically applied HCP were comparable to the published human data. We suggest that pig may be a suitable animal model for studying the percutaneous absorption of antimicrobial drugs.     

Acute toxicity of T2 toxin in rats, mice, guinea pigs, and pigeons

The acute intravenous, intragastric, subcutaneous, intraperitoneal and intratracheal toxicity of T2 toxin has been studied in rats, mice, guinea-pigs, and pigeons. The acute LD50 values obtained varied between 1.0 and 14 mg X kg-1, there being little difference between the various routes in any given species. T2 caused vomiting in pigeons at doses of one fifth or less the LD50. In rats doses of 3.0 and 5.0 mg X kg-1 T2 produced lymphopenia, reticulocytosis, and in the highest dose groups normoblastaemia. Additionally, changes in plasma alkaline phosphatase and aspartate aminotransferase activities were seen. Histological changes were observed in lymphoid organs and were most severe in the thymus, lymph nodes, and Peyer's patches. The spleen was less severely affected. Gastrointestinal changes consisting of dead and dying lymphoid cells throughout the lamina propria were seen together with, in some cases, mucosal ulceration. The time course of the development and of the reversal of the changes was followed.     

In vitro metabolism of an antiallergic agent, emedastine difumarate, in rats and guinea pigs

In order to clarify the interspecies differences in the metabolism of emedastine difumarate (KG-2413), in vitro metabolism was studied with liver preparations of rats and guinea pigs. The activities of hydroxylase, N-oxidase and N-demethylase, of emedastine were evaluated with liver 9000 x g supernatant and microsomes. As the results, the orders of activities were as follows; 5-hydroxylase greater than or equal to N-oxidase greater than 6-hydroxylase greater than N-demethylase in rats, and N-oxidase much greater than N-demethylase greater than 6-hydroxylase greater than 5-hydroxylase in guinea pigs. Emedastine N-oxide, little excreted into the urine of rats, was largely formed in vitro, so it was assumed that N-oxide reduction was important in vivo. The reductase activity of emedastine N-oxide was evaluated, and compared with N-oxidase activity of emedastine. In rats, the reductase activity was nearly equal to the N-oxidase activity, and relatively high even under aerobic conditions. On the other hand, in guinea pigs, the reductase activity was lower than the N-oxidase activity. It was considered that relative activities of the N-oxidation of tertiary amine in a 1,4-diazepine ring of emedastine and the reduction of N-oxide once formed were one of the factors of interspecies differences of metabolism of emedastine in rats and guinea pigs.     

Pharmacokinetics of bupropion and metabolites in plasma and brain of rats, mice, and guinea pigs

Recent reports indicate that bupropion, a novel non-tricyclic antidepressant, is metabolized differently in certain species of animals. To further define the disposition of bupropion, a study was done involving three species, the rat, mouse, and guinea pig, as animal models to evaluate bupropion metabolism. The pharmacokinetic profiles of bupropion and its major basic metabolites, BW 306U and BW A494U, were determined following the ip administration of 40 mg/kg bupropion to these animals. Pharmacokinetic profiles of the parent drug and metabolites from plasma and brain samples were obtained using a liquid chromatographic procedure. Further investigation of the reduced bupropion metabolite BW A494U was carried out by the ip administration of this metabolite to these animals and assaying the plasma and brain samples 90 min after dosing. Analysis of the pharmacokinetic data revealed that the rat quickly metabolized bupropion, but no basic metabolites accumulated. The mouse metabolized bupropion predominantly to BW 306U, whereas the guinea pig converted bupropion to reduced bupropion (BW A494U) as well as BW 306U. Brain/plasma ratios of bupropion among these animals did not vary significantly. However, both metabolites showed dramatic differences in their brain/plasma ratios among these species. When reduced bupropion (BW A494U) was injected, almost 3% of the plasma concentration of BW A494U was determined to be bupropion in the rat. Lesser amounts were converted in the mouse and guinea pig. Therefore, we have demonstrated that distinct differences exist in the metabolism of bupropion in various species of animals. The guinea pig, when compared to the rat or mouse, appears to constitute a model that most closely resembles that of human bupropion metabolism.     

盐酸二氢埃托啡对小鼠、大鼠和豚鼠肠道平滑肌的作用

目的：研究ＤＨＥ对肠道平滑肌的作用。方法：小鼠、大鼠和豚鼠离体和在体肠道平滑肌上，以吗啡为对照，比较ＤＨＥ与吗啡对肠道平滑肌作用的异同。结果：吗啡和ＤＨＥ减慢小鼠肠推进运动的ＥＤ５０分别为２．７９ｍｇ·ｋｇ－１和３．２３μｇ·ｋｇ－１；ＤＨＥ３６～６０μｇ·ｋｇ－１ｓｃ可松弛小鼠在体肠道平滑肌，在相同的实验条件下，吗啡５～２０ｍｇ·ｋｇ－１ｓｃ可剂量依赖性地收缩小鼠在体肠道平滑肌；在小鼠、大鼠和豚鼠离体肠管上，ＤＨＥ兴奋肠道平滑肌的浓度依次为１０～１００，０．１～１０和１０～１００μｍｏｌ·Ｌ－１，吗啡兴奋肠道平滑肌的浓度分别为０．１～１０，０．００２～２．０和０．１～１０μｍｏｌ·Ｌ－１，而ＤＨＥ兴奋肠道平滑肌的浓度是在镇痛剂量下体内无法达到的。结论：对肠道平滑肌作用，ＤＨＥ与吗啡不同，ＤＨＥ呈舒张效应，而吗啡为收缩效应。     

Excretion of phenazopyridine and its metabolites in the urine of humans, rats, mice, and guinea pigs

The metabolism of the urinary tract analgesic phenazopyridine [2,6-diamino-3-(phenylazo)pyridine; PAP] was studied in the urine of humans, rats, mice, and guinea pigs. Urinary excretion was rapid in human and guinea pig, but in the rat and mouse it was slower and there was significant fecal excretion. Metabolism of PAP was extensive in all four species, and there were marked quantitative differences in the routes of metabolism. The extent of azo bond cleavage was high in the mouse and guinea pig, moderate in the rat, and low in humans. Hydroxylation of both the phenyl and pyridyl rings of PAP was observed in all species. In the human, 5-hydroxyl PAP was the major metabolite (48.3% of the dose). It was concluded that there are marked species differences in the metabolism of PAP, and that none of the species studied resembles the human; the rat comes closest, but cannot be considered a particularly good model.     

Relationship between liver injury and transglutaminase activities in guinea pigs and rats

We investigated the effect of transglutaminase (TGase) on in guinea pigs and rats. Serum alanine aminotransferase (ALT) level increased 1 d after CCl(4) treatment of both in guinea pigs and rats since TGaese activity was greatly higher in guinea pigs than rats. However, serum ALT level in guinea pigs was very much lower than that in rats. Liver TGase activities decreased after CCl(4) treatment in both guinea pigs and rats. However, TGase activities in the liver from guinea pigs were higher than that from rats. Decreased TGase activities by CCl(4) in the liver from guinea pigs and rats were significantly recovered by retinoic acid treatment that was reported to increase TGase. Degree of recovery of serum ALT level by retinoic acid in rats was larger than in guinea pigs. These results suggested that the distinction of the effect of retinoic acid on serum ALT level in CCl(4)-treated animals was due to the different TGase activity that increased membrane stability.     

Cathartic activity of spasmogens in mice, rats and guinea pigs (author's transl)

To examine the effect of spasmogens on propulsive motility in the intestine, cathartic activity of drugs was investigated. Mice, rats and guinea pigs were individually observed in cages with 20 separate small rooms in which a sheet of filter paper covered the botton of case for observation of feces. The effect was evaluated 1 hr after drug administration. Cathartic activity of spasmogens was the most marked in mice followed by rats, but was rarely observed in guinea pigs. Cholinergic drugs and cholinesterase inhibitors had a cathartic effect in mice and rats, but the activity differed. Drugs such as acetylcholine and physostigmine produced a low cathartic activity even at sublethal and lethal doses. Other drugs as bethanechol, pilocarpine and neostigmine had a dose dependent cathartic effect at doses below lethal ones and were found to be clinically useful for intestinal relaxation after laparotomy. Among autacoids which contract the intestine by direct action on smooth muscles, histamine and bradykinin had no cathartic effect in mice and rats. 5-HT and prostaglandin E2 were dose dependent with a marked cathartic effect in both species. 5-HTP produced the same cathartic activity as that seen with 5-HT in mice, but had no cathartic effect in rats. The cathartic effect of BaCl2 was low, but dose dependent in both species. We recommend this method for the study of the effect of various compounds on the propulsive motility of the intestine.     

Paraquat disposition in rats, guinea pigs and monkeys

LD50 doses of ¹⁴C-labeled paraquat were administered to rats, guinea pigs and monkeys by gavage, and radioactivity was determined in excreta and tissues. Rat urine was analyzed for paraquat metabolites by thin-layer chromatography. [¹⁴C]Paraquat was absorbed from the gastrointestinal tract and reached highest serum values 0.5–1 hr after administration. Disappearance of [¹⁴C]paraquat from serum was characterized by a rapid initial decline followed by a prolonged slow decline. Tissue paraquat values were higher than serum values in rats and guinea pigs. Relative to other tissues, paraquat accumulated transiently in the lung and reached peak concentration 32 hr after administration. In rats a major portion of administered paraquat was not absorbed from the gastrointestinal tract. At 32 hr after paraquat, 52% of the administered dose remained in the gastrointestinal tract and 17 and 14% of the administered dose was excreted in the feces and urine, respectively. No radioactivity was recovered in expired air or flatus. Excretion of paraquat in urine and feces was prolonged in all species. In monkeys paraquat was measured in urine and feces 21 days after administration. Chromatography of urine from [¹⁴C]paraquat-treated rats revealed no metabolites. The primary pathologic changes induced by paraquat in the lung may be related to the transient uptake of the chemical by that organ.