Peroxisomal Catalase Activity Research Articles

Peroxisomal β-oxidation activity and catalase activity during development and aging in mouse liver

Liver peroxisomal β-oxidation activity on stearate, oleate, linoleate and α-linolenate was investigated as a function of age in two mouse strains. Each fatty acid showed a similar β-oxidation activity pattern with age characterized by a rapid increase (200%) from day 2 to 20 followed by a dramatic weaning-related decrease (70%) from day 20 to 22. There was a new increase (260%) from day 22 to 75, then a plateau up to day 300 days, and finally an age-related decrease (70%) from day 300 to 540. Oleic, linoleic and α-linolenic acids were respectively 5-, 7.5- and 9-fold more degraded than stearic acid. Catalase specific activity showed the same age-related pattern as fatty acid β-oxidation. Both mouse strains showed the age-related decreases. The longer-lived strain exhibited higher activity for both peroxisomal β-oxidation and catalase and the rate of decrease of these two activities during aging was the same for both strains. The catalase/α-linolenic acid β-oxidation ratio was constant during adulthood and aging. These results suggest that peroxisomal β-oxidation and catalase activities are closely related throughout and implications for long-chain and very long-chain fatty acid metabolism, maintenance of membrane fatty acid composition and anti-oxidant status during aging are discussed.

Dehydroepiandrosterone is a complete hepatocarcinogen and potent tumor promoter in the absence of peroxisome proliferation in rainbow trout.

Dehydroepiandrosterone (DHEA), fed for 30 weeks to rainbow trout after initiation with the hepatocarcinogen aflatoxin B1 (AFB1), produced a dose-dependent enhancement of carcinogenesis as measured by increased tumor incidence, multiplicity and size. Significant enhancement was observed at 222 p.p.m., which corresponds to a daily dosage one-half that previously administered to humans in clinical trials. DHEA was also capable of acting as a complete carcinogen in this model, producing liver tumors at doses as low as 222-444 p.p.m. Tumors isolated from trout treated with DHEA alone contained mutations in Ki-ras, primarily codon 12[1] G-->A transitions, providing the first suggestive evidence that DHEA could be a genotoxic carcinogen. The carcinogenicity of DHEA in trout is independent of peroxisome proliferation, as measurements of peroxisomal beta-oxidation and catalase activity support previous observations that trout, like humans, are weak responders to peroxisome proliferators.

Influence of pantothenic acid deficient diet on the metabolic changes in rats exposed to bezafibrate and di-(2-ethylhexyl)phthalate

The present study was undertaken to examine the influence of pantothenic acid deficient diet on the metabolic responses to peroxisome proliferators including bezafibrate and di-(2-ethylhexyl)phthalate (DEHP). The growing rats were fed on the pantothenic acid deficient diet with or without addition of 0.1% bezafibrate or 0.5% DEHP for 14 days. Feeding of pantothenic acid deficient diet decreased food intake and growth rate. Dietary addition of these chemicals caused the earlier onset of growth retardation by pantothenic acid deficient diet. These chemicals increased hepatic total Coenzyme A (CoA) levels, associated with increased activities of hepatic peroxisomal β-oxidation and catalase. These increments in hepatic total CoA and activities of these enzymes were all depressed by pantothenic acid deficient diet. The results suggest that an increased hepatic CoA pool by the proliferators might relate to the induction of peroxisome β-oxidation and catalase, and be an adaptive response to exposure to the proliferators.

Peroxisomes in liver, heart, and kidney of mice fed a commercial fish oil preparation: original data and review on peroxisomal changes induced by high-fat diets.

Male NMRI mice were fed a diet with 10% w/w Beromegan for up to three weeks. Beromegan is a commercial fish (salmon) oil preparation rich in eicosapentaenoic acid and docosahexaenoic acid. Peroxisomal beta-oxidation capacity, catalase activity, and ultrastructural morphometry of the hepatic peroxisomes were investigated. In myocardium and kidney, catalase activity, peroxisomal staining after catalase cytochemistry, peroxisomal morphology, and morphometry (in myocardium) were evaluated. In liver, we found a significant increase in peroxisomal beta-oxidation, catalase activity, and peroxisomal number already after 3 days of dietary treatment. These changes were more pronounced after 3 weeks. Peroxisomal size was not changed. Positive correlations were found between peroxisomal enzyme activities and the number but not the size of the peroxisomes, and between catalase activity and beta-oxidation capacity. The mean peroxisomal diameter per animal was inversely proportional to catalase activity measured in homogenate. In myocardium, catalase activity was increased with duration of fish oil feeding. Peroxisomal staining, number, and size were also increased when compared to controls. In kidney, no alterations were observed. Our results indicate a beneficial effect of a diet supplemented with fish oil on the peroxisomal metabolism in liver and myocardium; it differs from the changes induced by xenobiotic peroxisome proliferation.

Comparison of the potencies of (+)‐ and (−)‐2‐ethylhexanoic acid in causing peroxisome proliferation and related biological effects in mouse liver

Male C57BL/6 mice were exposed to 1% (w/w) (+)- or (-)-2-ethylhexanoic acid or an equimolar mixture of these enantiomers in their diet for 4 or 10 days. A significant increase in liver weight and a 2- to 3-fold increase in the protein content of the mitochondrial fraction were seen in all cases. Peroxisomal palmitoyl-CoA oxidation was increased 2- to 3.5-fold after 4 days of treatment and 4- to 5-fold after 10 days, while the corresponding increases in peroxisomal lauroyl-CoA oxidase activity were 2- to 3-fold and 9- to 12-fold, respectively. Peroxisomal catalase activity was unchanged, whereas the microsomal and cytosolic activities were increased 2- to 3-fold and 6- to 16-fold, respectively. These treatments also induced microsomal omega-hydroxylation of lauric acid 7-fold and soluble epoxide hydrolase activity in the mitochondrial and cytosolic fractions, as well as microsomal epoxide hydrolase activity about 50-100%. The only significant differences observed between the effects of (+)-2-ethylhexanoic acid and its (-)-enantiomer were on peroxisomal palmitoyl-CoA oxidation and lauroyl-CoA oxidase activity after 4 days of treatment. In both these cases the (+)-enantiomer resulted in increases which were 50-75% greater than those seen with the (-)-form.

Structure-activity relationships for induction of peroxisomal enzyme activities in primary rat hepatocyte cultures

Rat hepatocytes were cultured for 70 hr with a series of 15 chemicals (including herbicides and derivatives, hypolipidaemic agents and other compounds) and the effects on some enzyme activities were determined. All of the compounds produced concentration-related increases in the activities of peroxisomal fatty acid β-oxidation (palmitoyl-CoA oxidation), catalase, carnitine acetyltransferase and lauric acid 12-hydroxylase. Marked differences between the potencies of the compounds were observed but some correlations were obtained between the induction of palmitoyl-CoA oxidation and the other three enzyme activities measured. Quantitative structure-activity relationships (QSARs) were observed between the induction of palmitoyl-CoA oxidation and catalase activities and compound electronic structural parameters obtained by molecular orbital calculations (MINDO/3 method). In these studies both compound bulk molecular parameters and parameters of the free carboxyl group (present in all of the chemicals examined) were important in determining compound potencies. The existence of QSARs between biological activity and chemical structure for a series of peroxisome proliferators suggests that these compounds share a common mechanism of initiation of peroxisome proliferation in rodent liver. The data also demonstrate the usefulness of rat hepatocyte cultures for screening compounds for peroxisome proliferation and for investigating structure-activity relationships.

Perfluorooctane sulfonic acid is a potent inducer of peroxisomal fatty acid beta-oxidation and other activities known to be affected by peroxisome proliferators in mouse liver.

Perfluorooctane sulfonic acid is almost as potent as perfluorooctanoic acid in causing increases in peroxisomal fatty acid beta-oxidation, peroxisomal catalase activity, omega-hydroxylation of lauric acid, cytosolic epoxide hydrolase activity and cytosolic DT-diaphorase activity. Octane sulfonic acid was ineffective at doses used for perfluorooctane sulfonic acid and perfluorooctanoic acid. The results support the theory of co-regulation of these parameters and peroxisome proliferation. The fact that perfluorooctane sulfonic acid causes peroxisome proliferation challenges the hypothesis that the first step in this process is formation of a thioester between the proliferator (the carboxylic group) and coenzyme A.

Is the cytosolic catalase induced by peroxisome proliferators in mouse liver on its way to the peroxisomes?

Dietary treatment of male C57B1/6 mice with clolibrate, nafenopin or WY-14.643 resulted in a modest (at most 2-fold) increase in the total catalase activity in the whole homogenate and mitochondrial fraction prepared from the livers of these animals. On the other hand, the catalase activity recovered in the cytosolic fraction was increased 12- to 18-fold, i.e. 30–35% of the total catalase activity in the hepatic homogenate was present in the high-speed supernatant fraction after treatment with these peroxisome proliferators. A study of the time course of the changes in peroxisomal and cytosolic catalase activities demonstrated that the peroxisomal activity both increased upon initiation of exposure and decreased after termination of treatment several days after the increase and decrease, respectively, in the corresponding cytosolic activity. This finding suggests that the cytosolic catalase may be on its way to incorporation into peroxisomes.

Ischemia-reperfusion injury: Biochemical alterations in peroxisomes of rat kidney

Exogenously supplied catalase, a peroxisomal enzyme, has been found to be of therapeutic value in ischemic injury. Therefore, we examined the effect of ischemic-reperfusion injury on the structure and function of kidney peroxisomes. Ischemic injury changed the density of peroxisomes from 1.21 g/cm 3 (peak I) to a lighter density of 1.14 g/cm 3 (peak II). The number of peroxisomes moving from the normal density population (peak I) to a lower density population (peak II) increased with an increase in ischemic injury. Latency experiments indicated both populations of peroxisomes to be of intact peroxisomes. Immunoblot analysis with antibodies against peroxisomal matrix and membrane proteins demonstrated that after 90 min of ischemia a significant number of matrix proteins were lost in the peak II population, suggesting that functions of these peroxisomes may be severally affected. Reperfusion following ischemic injury resulted in loss of peroxisomal matrix proteins in both peaks I and II, suggesting that peroxisomal functions may be drastically compromised. This change in peroxisomal functions is reflected by a significant decrease in peroxisomal catalase activity (35%) and β-oxidation of lignoceric acid (43%) observed following 90 min of ischemia. The decrease in catalase activity was more pronounced in reperfused kidneys even after a shorter term of ischemic injury. Reperfusion restored the normal peroxisomal β-oxidation in kidneys exposed up to 60 min of ischemia. However, 90 min of ischemia was irreversible as there was a further decrease in β-oxidation upon reperfusion. The decrease in catalase activity during ischemia alone was due to the formation of an inactive complex, whereas during reperfusion, following 90 min of ischemia, inactivation and proteolysis or decreased synthesis of catalase contributed equally toward the injury. The observed changes in the structure and function of peroxisomes as a result of ischemic-reperfusion injury and the ubiquitous distribution of peroxisomes underlines the importance of this organelle in the pathophysiology of vascular injury in general.

Effects of the peroxisome proliferators ciprofibrate and perfluorodecanoic acid on hepatic cellular antioxidants and lipid peroxidation in rats

The purpose of this study was to determine if hepatic cellular antioxidants and indices of oxidative damage are altered by administration of the peroxisome proliferators ciprofibrate and perfluorodecanoic acid (PFDA). Rats were fed 0.01% ciprofibrate in the diet or were injected with PFDA (0.5 or 5.0mg/kg, i.p.) every 4 weeks for 6, 14, 30, 54, and 78 weeks. Peroxisomal fatty acyl-CoA oxidase and catalase activities were increased by both ciprofibrate and PFDA throughout the study. Neither ciprofibrate nor PFDA increased the levels of malonaldehyde or conjugated dienes, but ciprofibrate decreased these indices at early time points. Ciprofibrate decreased the following cellular antioxidants or antioxidant enzymes: vitamin C, vitamin D, DT-diaphorase, glutathione peroxidase, glutathione- S-transferase, and glutathione reductase; Superoxide dismutase and glutathione were not affected. PFDA decreased DT-diaphorase and increased Superoxide dismutase, but did not affect other cellular antioxidants. This study shows that administration of the peroxisome proliferators ciprofibrate and PFDA did not increase indices of lipid peroxidation, but that cellular antioxidant defenses were inhibited for a prolonged period of time by the peroxisome proliferator ciprofibrate.

Degradation of peroxisomal catalase in an n-alkane-utilizable yeast, Candida tropicalis

A drastic decrease in the activities of peroxisomal enzymes, catalase and acyl-CoA oxidase, was observed when an n-alkane-assimilating yeast, Candida tropicalis, was transferred from an n-alkane medium into a glucose medium. The level of the activity of catalase, one of the peroxisomal enzymes inducibly synthesized in harmony with the development of peroxisomes, decreased parallelly with the disappearance of peroxisomes. Degradation of catalase in peroxisomes is suggested to consist of two processes as a result of the transfer experiments of cells in the presence and absence of cycloheximide. One is a process independent of protein synthesis de novo, while the other is a process dependent on protein synthesis de novo. Within 1 h after transfer, it was noticeable that the decrease in the level of mRNA encoding catalase occurred more drastically than that in the catalase activity. Western blot analysis using anti-catalase antiserum after subcellular fractionation demonstrated that degradation products of catalase were present in peroxisomes before and even after transferring cells from the alkane medium into the glucose medium. These facts suggest that peroxisomes might have a certain inherent system of proteolysis, related to the turnover of peroxisomal proteins, and that this system would continue to operate without protein synthesis de novo after rapid repression of the synthesis of mRNA encoding catalase. Finally, catalase seemed to be further degraded with proteases of vacuoles synthesized de novo, the catalase activity reaching a house-keeping level.

Peroxisomal oxidases and catalase in liver and kidney homogenates of normal and di(ethylhexyl)phthalate-fed rats

1. 1. Activities of peroxisomal oxidases and catalase were assayed at neutral and alkaline pH in liver and kidney homogenates from male rats fed a diet with or without 2% di(2-ethylhexyl)phthalate (DEHP) for 12 days. 2. 2. All enzyme activities were higher at alkaline than at neutral pH in both groups. 3. 3. The effect of the DEHP-diet on the peroxisomal enzymes was different in kidney and liver. Acyl-CoA oxidase activity was raised three-and sixfold in kidney and liver homogenates, respectively. The activity of d-amino acid oxidase decreased in liver, but increased in kidney homogenates. In liver homogenates, urate oxidase activity was not affected by the DEHP diet. The catalase activity was twofold induced in liver, but not in kidney. 4. 4. The differences suggest that the changes of peroxisomal enzyme activities by DEHP treatment are not directly related to peroxisome proliferation. 5. 5. DEHP treatment caused a marked increase of total and peroxisomal fatty acid oxidation in rat liver homogenates. 6. 6. In the control group the rate of peroxisomal fatty acid oxidation was higher at alkaline pH than at neutral pH. 7. 7. This rate was equal at both pH values in the DEHP-fed group, in contrast to the acyl-CoA oxidase activity. These results indicate that after DEHP treatment other parameters than acyl-CoA oxidase activity become limiting for peroxisomal β-oxidation.

Effects of Prolonged Treatment with Phthalate Ester on Rat Liver

Rats were fed a diet containing 2%, 0.2% or 0.02% di(2-ethylhexyl)phthalate (DEHP) for a period of 102 weeks. Only the 2% diet caused a substantial decrease in body weight. Both peroxisomal palmitoyl-CoA dehydrogenase and mitochondrial carnitine acetyltransferase activities were greatly induced by exposure to the highest dose of phthalate ester, reaching maximal plateau values after about 20 weeks of treatment. The diet containing 0.2% DEHP increased both activities slowly, but continuously, and at the end of the two-year period these increases were almost comparable to those obtained with the highest dose. Even the lowest dose gave a slowly increase in these activities. Both microsomal NADPH-cytochrome c reductase activity and the level of cytochrome P-450 were increased initially by exposure to 2% DEHP, but returned almost or completely to the control level after about 30 weeks of exposure. Depending on the dose of DEHP in the diet, peroxisomal catalase activity was elevated above the control level during the first year of treatment but was about the same as in the control animals during the second year. A substantial decrease in peroxisomal urate oxidase activity was observed throughout the entire experimental period. When treatment was ceased after one year, all activities returned to the control values within 2-3 weeks. These results demonstrate the complex nature of the effects caused by prolonged treatment with DEHP with cumulative increases at low doses.

Hepatic steatosis in zebra fish ( Brachydanio rerio) induced by long-term exposure to γ-hexachlorocyclohexane

In a full life cycle test, newly hatched eggs of zebra fish, Brachydanio rerio, were reared to sexual maturity under continuous exposure to 40, 80, 110, 130, and 150 μg/liter lindane, γ-hexachlorocyclohexane. The effects of lindane were investigated by recording behavior and survival of the F 0- and F 1-generation as well as morphological alterations in liver ultrastructure of F 0. Changes in peroxisomes were visualized by cytochemical staining for catalase activity with diaminobenzidine. Whereas behavioral changes can already be observed at 40 μg/liter, survival and number of eggs in F 0 as well as survival and growth of F 1 are unaffected by up to 80 μg/liter lindane. At concentrations ⩾ 110 μg/liter, survival of larvae is reduced already after 35 days, and mortality is 100% after 3 months. From 40 μg/liter, liver ultrastructure displays a microvesicular fatty vacuolation (steatosis) characterized by lipid deposition within the cisternae of the RER. At 40 μg/liter, this highly specific pathological change is accompanied by accumulation of hepatic macrovesicular triglyceride droplets, glycogen depletion, and the occurrence of club-shaped mitochondria. Additional alterations at 80 μg/liter comprise proliferation of SER in males and progressive fractionation of RER in females, stacking of club-shaped mitochondria, a conspicuous decrease in peroxisomal catalase activity, infiltration of macrophages into the liver parenchyma, and a significant stimulation of hepatocytic mitosis. Among several substances tested so far in zebra fish (4-nitrophenol, 4-chloroaniline 3,4-dichloroaniline, atrazine, lindane), lindane is the only compound inducing behavioral changes and hepatic steatosis in conjunction with a reduction in fertility. With regard to the relative sensitivity of the methods applied, behavioral and cytological studies appear more responsive to lindane exposure than survival studies.

Induction of peroxisomal enzymes in cultured porcine endothelial cells by the hypolipidemic drug ciprofibrate

The purpose of this study was to determine if the hypolipidemic peroxisome proliferator ciprofibrate, which induces peroxisomes in the liver, can induce peroxisomes in cultured porcine pulmonary endothelial cells. Ciprofibrate was added at three concentrations to cell cultures for a 6-day period. The induction of peroxisomes in the cells was detected by determining total peroxisomal beta-oxidation and peroxisomal catalase activity. The addition of ciprofibrate was found to increase peroxisomal enzyme activities in a dose-dependent manner, with the highest activity being reached at 1000 microM ciprofibrate. Ciprofibrate also caused an increased transfer of albumin across endothelial cells cultured on micropore filters. This study shows that peroxisomal enzyme activities can be induced by ciprofibrate in endothelial cells, which may have implications in diseases mediated by vascular injury.

Effect of Vitamin E on Linoleic Acid-Mediated Induction of Peroxisomal Enzymes in Cultured Porcine Endothelial Cells

Linoleic acid decreases endothelial barrier function in culture. We hypothesize that the mechanism may involve induction of peroxisomes, with subsequent generation of hydrogen peroxide, and that vitamin E may protect against barrier function loss by preventing the induction of peroxisomal enzymes. To investigate this hypothesis, we exposed cultured endothelial cells to 0 or 90 mumols/L linoleic acid [18:2(n-6)], with or without 25 mumols/L supplemental vitamin E, for 5 d. The induction of peroxisomes by linoleic acid exposure was determined by measuring cellular peroxisomal beta-oxidation and catalase activity. Vitamin E alone had no effect on beta-oxidation or catalase activity, whereas linoleic acid exposure significantly increased both compared with control values. Vitamin E supplementation prevented induction of peroxisomal beta-oxidation and catalase activity by 18:2. In contrast, cell enrichment with vitamin E had no effect on 18:2-induced accumulation of cytoplasmic lipid-like droplets. These results confirm our hypothesis that the protective effects of vitamin E against fatty acid-mediated endothelial cell injury may be due in part to the ability of vitamin E to prevent the induction of peroxisomal beta-oxidation enzymes and thus the formation of excess hydrogen peroxide.

The hypolipidemic peroxisome-proliferating drug, bis(carboxymethylthio)-1.10 decane, a dicarboxylic metabolite of tiadenol, is activated to an acylcoenzyme A thioester

Bis(carboxymethylthio)-1.10 decane (BCMTD), a thiodicarboxylic acid, was shown to be a hypolipidemic peroxisome-proliferating drug as it: (a) decreased the total serum triacylglycerols and cholesterol; (b) induced hepatomegaly; (c) increased the peroxisomal β-oxidation and catalase activity and the activities of the multiorganelle localized enzymes: palmitoyl-CoA synthetase, palmitoyl-CoA hydrolase, glycerophosphate acyltransferase; (d) decreased the carnitine palmitoyltransferase and urate oxidase activities; and (e) induced the bifunctional eonyl-CoA hydratase in peroxisomes. The present study has confirmed the effect of tiadenol administration on the activities of key enzymes involved in hepatic fatty acid metabolism in male rats. However, the hepatic pleiotropic response was more marked with the dicarboxylic acid than with its alcohol. In a separate dose-response study BCMTD was found to be a more potent inducer of peroxisomal β-oxidation compared to tiadenol. BCMTD can be activated in vitro to its coenzyme A thioester by a dicarboxyl-CoA synthetase. In control and BMCTD-treated animals, the synthetase activity was found in all cullular fractions except the cytosolic. Whether the acyl-CoA thioesters of peroxisome-proliferating drugs may be mediators of peroxisomal proliferation should be considered.

Congenital rubella syndrome associated with calcific epiphyseal stippling and peroxisomal dysfunction

An infant girl had the clinical and immunologic findings of congenital rubella syndrome but also had arthrogryposis multiplex and calcific epiphyseal stippling. Spastic quadriparesis developed, and both physical and behavioral development were slow. Increased spasticity of the legs at 5 1/2 years was related not to progressive rubella encephalomyelopathy but to spinal cord compression by abnormal cartilaginous tissue. The presence of a peroxisomal disorder was demonstrated by a greatly increased level of phytanic acid and slightly increased levels of hexacosanoate in serum and by reduced activity of peroxisomal dihydroxyacetone phosphate acyltransferase and a slightly increased ratio of cytosolic to peroxisomal catalase activity in cultured fibroblasts. A reduction in the number and size of peroxisomes was demonstrated in cultured fibroblasts, and a needle biopsy specimen of the liver also showed the peroxisomes to have a smaller diameter than usual. We recommend that any child with epiphyseal stippling be assessed for peroxisomal disease and that the potential for spinal cord compression by dysplastic bone or cartilage be recognized. The association of peroxisomal dysfunction with congenital rubella has not been described previously. The interaction between rubella virus infection and peroxisomal function may need further investigation.

Alkylthioacetic acid (3-thia fatty acids) — a new group of non-β-oxidizable, peroxisome-inducing fatty acid analogues. I. A study on the structural requirements for proliferation of peroxisomes and mitochondria in rat liver

The induction of peroxisome proliferation was examined in rat liver after administration of equal concentrations (1 mmol/kg body weight) of 1,10-bis(carboxymethylthiodecane) (BCMTD), 1-mono(carboxymethylthiotetradecane) (CMTID), 1-mono(carboxymethylthiooctane) (CMTO), 1-mono(carboxyethylthiotetradecane) (CETTD), palmitic acid and hexadecanedioic acid (HDDA). BCMTD, a non-β-oxidizable and non-ω-oxidizable sulphur-substituted fatty acid analogue was considerably more potent than CMTTD (only non-β-oxidizable) in inducing enlargement of the liver and increasing peroxisomal activities (monitored by peroxisomal β-oxidation, palmitoyl-CoA hydrolase and catalase activities). Morphometric analysis of randomly selected hepatocytes revealed that BCMTD and CMTTD treatment increased the number and size of peroxisomes and the relative volume fraction of the peroxisomes. All these cellular responses were more marked with BCMTD than compared with CMTTD. CMTO, a non-β-oxidizable fatty acid analogue containing a lower hydrophobic alkyl-end than CMTTD and CETTD (a β-oxidizable fatty acid analogue), showed a slight increase (1.4–1.8-fold) of peroxisomal β-oxidation and caused marginally morphological changes of peroxisomes compared with CMTTD and BCMTD. The most striking effect of the alkylthiopropionic acid (CETTD) was an enhancement of the hepatic triacylglycerol level. Palmitic acid and hexadecanedioic acid only marginally affected the peroxisomal activities, but no morphological changes of peroxisomes and fat droplets were observed. The presented data strongly suggest that a minimal structural requirement for a peroxisome proliferator may be (1) a carboxylic acid group linked to (2) a hydrophobic backbone which (3) cannot be β-oxidized i.e., the fatty acid analogues have a sulphur atom in the β-position. It is also conceivable that blockage for ω-oxidation may potentiate the peroxisome-proliferating activities in as much as BCMTD was more potent than CMTTD. Two mitochondrial marker enzymes, carnitine palmitoyltransferase and succinate phenazine methosulphate oxidoreductase were differently affected after administration of the investigated compounds. Furthermore, BCMTD and CMTTD as well as HDDA treatments increased the number of mitochondria, but the mitochondria tended to be smaller. The overall results presented here indicate that the structural requirements for proliferation of mitochondria are not identical to those for proliferation of peroxisomes.

Response of the jejunal mucosa of dogs with aerobic and anaerobic bacterial overgrowth to antibiotic therapy.

Dogs with naturally occurring aerobic or anaerobic bacterial overgrowth have been examined before and after antibiotic therapy in order to assess reversibility of damage to the jejunal mucosa. Histological changes in peroral jejunal biopsies were relatively minor before and after treatment, but sucrose density gradient centrifugation revealed specific biochemical abnormalities that responded to antibiotic therapy. Aerobic overgrowth was initially associated with a marked loss of the main brush border component of alkaline phosphatase activity; this recovered following treatment, suggesting that aerobic bacteria may cause reversible damage to the hydrophobic region of the brush border membrane. In contrast, anaerobic overgrowth was initially associated with a marked reduction in brush border density, indicative of a considerable fall in the glycoprotein-to-lipid ratio of the membrane. Density increased from 1.17 to 1.21 g/ml after antibiotic therapy, consistent with recovery from this relatively severe damage to the brush border caused by anaerobic bacteria. Reductions in soluble and peroxisomal catalase activities which could compromise mucosal protection against free radicals in dogs with aerobic overgrowth, and a loss of particulate malate dehydrogenase activity indicative of mitochondrial disruption in dogs with anaerobic overgrowth, were also reversed after treatment. These findings indicate that aerobic and anaerobic bacterial overgrowth can result in contrasting but potentially reversible damage to the jejunal mucosa which would not be detected by conventional investigative procedures.