Several aspects of mineral/protein nutrition in relation to consumption of an oil involved in the toxic syndrome

An oil involved in the 'toxic syndrome' and two similar mixtures of oils, one with and the other without added oleoanilides, were studied for their effects on the utilization of protein, calcium, magnesium, phosphorus, sodium, potassium and zinc. Forty-eight female Wistar rats initially weighing about 75 g were fed for 28 days on the same semi-synthetic diet containing: virgin olive oil, or a mixture of canbra oil (50%), refined olive-pomace oil (20%), grapeseed oil (20%) and animal fat (10%), or the same dietary mixture supplemented with either 700 ppm oleoanilides or the alleged toxic oil. Weight, food intake and nutritional balances were monitored. The food intake of the animals fed the toxic oil began to decrease at the end of the trial, producing a reduction in the amount of nutrients ingested, but no weight loss. This oil also negatively affected the digestion of protein, potassium, sodium and zinc, the mechanism of which, in the case of the first two, appears to be related to the source of the fat. It also decreased metabolic utilization while favouring protein catabolism and the elimination of phosphorus, magnesium and potassium. No substantial modifications were noted in the animals' bones.     

东宝肝泰对大鼠高脂饮食脂肪性肝炎的预防作用

目的：探讨东宝肝泰对大鼠高脂饮食脂肪性肝炎的预防作用。方法：雄性SD大鼠24只，随机分为3组。正常组予标准饮食喂养；对照组予高脂饮食(普通饲料加20g／kg胆固醇加100g／kg猪油)喂养；预防组在高脂饮食喂养8周后加用东宝肝泰，均于第16周处死。测量大鼠体重、肝湿重、肝指数(肝湿重／体重)及脂肪重量，并测定血清脂质、肝功能和肝匀浆脂肪含量，通过HE染色观察肝细胞脂肪变性、炎症程度。结果：预防组和对照组大鼠均出现肥胖、高脂血症及血清转氨酶升高。与对照组相比，预防组各项指标均有改善趋势，但除血清天门冬酸氨基转移酶(AST)、总胆固醇(TC)外两组间比较并无统计学差异。结论：东宝肝泰对高脂饮食诱发的大鼠高脂血症性脂肪性肝炎可能无预防作用。     

Toxicological evaluation of mixtures of nonionic surfactants,alone and in combination with oil

The toxicity to human bronchial (16-HBE14o-) epithelium cells of nonionic surfactants, polyoxyethylene-10-oleyl ether (C(18:1)E(10)), polyoxyethylene-10-dodecyl ether (C(12)E(10)), and N,N-dimethyl-dodecylamine-N-oxide (C(12)AO) alone or in combination with a range of pharmaceutically acceptable oils (namely, ethyl esters and triglyceride oils), was determined with the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. Regardless of the presence of oil, all C(12)E(10)- and C(12)AO-containing systems were toxic at concentrations around or below their critical aggregation concentrations (as determined by surface tension measurements), suggesting that surfactant toxicity was due to the disruption caused by the partitioning of monomeric surfactant into the cell membrane. Systems prepared from C(18:1)E(10) alone or in combination with a low-molecular-weight oil, such as ethyl butyrate or tributyrin, were toxic above their critical aggregation concentration. In contrast, systems prepared from C(18:1)E(10) in combination with a high-molecular-volume oil (e.g., ethyl oleate, Miglyol 812, or soybean oil) were toxic only at concentrations significantly greater than their critical aggregation concentration, suggesting that in these cases surfactant toxicity was mediated by the aggregated form of the surfactant solubilizing components of the cell membrane. In the C(18:1)E(10)-stabilized system, it is proposed that toxicity was significantly reduced on incorporation of high-molecular-volume oils because these oils cause formation of a distinct oil core in the aggregates that leads to a reduction in the ability of the system to solubilize components of the cell membrane.     

The effect of dietary lipids and antioxidants on the activity of epoxide hydratase in the rat liver and intestine

The effect of varying the fatty acid composition of the lipid components of the diet on the activity of epoxide hydratase in the rat liver and intestinal mucosa has been studied. Feeding a 10% cod liver oil diet (containing 18% C20:5 and 11% C22:6) resulted in a 3-fold increase in epoxide hydratase activity in the liver and a 1.6-fold increase in the intestine compared to rats fed a fat-free diet. The activity of epoxide hydratase in rats fed a cod liver oil diet was significantly greater than that for the group fed a lard diet (containing mainly saturated and mono-unsaturated fatty acids) containing the same quantity of vitamin E. Thus, the enhancing effect of the cod liver oil diet was due to the polyunsaturated fatty acids in this oil. Dietary corn oil (58% C18:2) also stimulated epoxide hydratase activity in the liver but not in the intestine. Vitamin E levels of up to 500 mg/kg diet were ineffective at inducing epoxide hydratase activity in both the liver and intestine. Significant changes in the fatty acid composition of hepatic and intestinal microsomes took place when rats were fed diets of different fatty acid composition. These changes were such that the proportions of polyunsaturated fatty acids in the microsomal fractions reflected the amounts of these fatty acids in the dietary fat. Hepatic epoxide hydratase activity was found to be positively correlated to the proportion of polyunsaturated fatty acids in the microsomal fractions of the liver.     

Reproductive toxicology and nutritional studies on mahua oil (Madhuca latifolia)

Mahua (Madhuca latifolia, Sapotaceae) seed oil is a common ingredient of hydrogenated fat in India. It is obtained from the seed kernels (which contain 45% oil, w/w), and is a pale yellow, semi-solid fat at room temperature. It has palmitic (19%), stearic (15%), oleic (42%) and linoleic (24%) as a major fatty acids. The physicochemical parameters of the oil are similar to those of other edible oils. The unsaponifiable fraction contains several unidentified polyenes. Nutritional studies were carried out in groups of 15 weanling albino rats of each sex, fed for 14 wk on a 20% protein diet, adequate in all vitamins and minerals, containing 10% mahua oil. A similar (control) group was simultaneously maintained on the same basic diet containing 10% groundnut oil. The growth, fat absorption, and retention of nitrogen, calcium and phosphorus were similar in the two groups, as were the lipid profiles of the serum, liver and heart. Multigeneration reproduction studies in groups of 15 rats of each sex, fed a diet containing 10% mahua oil, as used in the above study, indicated poor reproductive performance in the second generation. All the male rats became sterile. Histological studies indicated bilateral testicular atrophy with degenerative changes in the seminiferous tubules in the affected animals. On withdrawal of mahua oil from the diet and rehabilitation, the male animals regained their fertility. These results indicate temporary male sterility on feeding mahua oil to rats. No other adverse toxicological effects were found.     

Effect of feeding blended and interesterified vegetable oils on antioxidant enzymes in rats

The present study was undertaken to evaluate the effect of feeding blended and interesterified oils prepared using coconut oil (CNO) with rice bran oil (RBO) or sesame oil (SESO), with a polyunsaturated/saturated (P/S) ratio of 0.8-1.0, on oxidative stress and endogenous antioxidant system. Feeding blended oils resulted in significantly increased hepatic lipid peroxide levels in rats given blended oil CNO + RBO or CNO + SESO by 1.3 and 1.6-fold, respectively compared to rats fed diet containing CNO. The lipid peroxide level in erythrocyte membrane also increased in rats fed blended oil compared to rats fed with CNO. Rats fed interesterified oils prepared from these blended oils also showed increased lipid peroxide level compared to rats given CNO diet, however it was not significantly different from rats fed with their respective blends. There was a significant increase in the activity of endogenous antioxidant enzymes super oxide dismutase, catalase, glutathione peroxidase and glutathione-s-transferase after feeding blended and interesterified oils. The activities of Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase were increased in rats fed blended and interesterified oils. These results indicated that the P/S ratio of dietary fat is an important factor in determining the oxidative stress, activity of endogenous antioxidant enzymes and activity of membrane bound enzymes.     

Novel approach to diet design for determining macronutrient preference.

Previous studies indicate that rats fed a saturated vs. unsaturated fat consume more of a high-protein/low-carbohydrate and less of a low-protein/high-carbohydrate diet. Present studies were conducted to determine whether saturated-fat-fed rats are preferring protein or avoiding carbohydrate. Three combinations of diets were prepared in which one macronutrient was held constant and two covaried: 1) high protein/low carbohydrate and low protein/high carbohydrate, 2) high fat/low carbohydrate and low fat/high carbohydrate, and 3) high fat/low protein and low fat/high protein. Male Sprague-Dawley rats (75-99 g) were fed either 34% tallow (n = 30) or corn oil (n = 30) diets for 4 days. These diets were removed and one third of each group was given one of the diet combinations. Rats previously fed tallow consumed more high-protein/low-carbohydrate and low-carbohydrate/high-fat diets and less high-carbohydrate/low-fat diet than controls previously fed corn oil. These data suggest that tallow-fed animals are avoiding carbohydrate rather than preferring protein.     

Evaluation of jojoba oil as a low-energy fat. 2. Intestinal transit time, stomach emptying and digestibility in short-term feeding studies in rats

The influence of jojoba oil (JO) incorporation in the diet on stomach emptying and intestinal transit time, and the digestion and absorption of JO were investigated in short-term feeding studies in rats. The animals were fed purified diets containing 18% (w/w) fat, of which half consisted of a mixture of lard and sunflower seed oil (SF) supplemented with an equivalent amount of JO. The control animals were fed a mixture of lard and SF (18%). No treatment-related differences were observed in the rate of stomach emptying or the intestinal transit time. Comparative lipid analysis of lymph, intestinal content, intestinal mucosa and faeces indicated that most of the ingested JO was degraded and absorbed. Part of the JO was present as wax ester in the lymph. Hydrolysis of JO was much slower than that of triacylglycerols and continued in the alimentary tract beyond the small intestine due to bacterial processes. JO did not influence the absorption of the conventional fat.     

Avocado oils and hepatic lipid metabolism in growing rats

The effect of various avocado oils on liver metabolism was studied in growing female rats. The rats were fed diets containing 10% (w/w) avocado oil for 4 wk. In comparison with rats fed refined avocado oil obtained from cored fruit by centrifugal separation, rats fed unrefined avocado oil obtained by organic solvent extraction from intact fruit, or its unsaponifiable components, showed a significant increase in total liver lipogenesis as well as in phospholipid and triglceride synthesis. Rats fed avocado-seed oil exhibited enhanced [1-14C]acetate incorporation into total liver lipids but showed the same distribution of label in the three main lipid classes as that of rats fed refined avocado oil. In addition, a significant reduction of triglycerides and protein content of plasma very-low-density lipoprotein and high-density lipoprotein fractions was observed in rats fed avocado-seed oil as compared with rats fed refined oil. Electron micrographs suggested that the alterations in hepatic lipogenesis are related to the marked proliferation of the smooth endoplasmic reticulum, which is known to be associated with induction of enzymes involved with lipid biosynthesis. The differences between the animals fed seed oil and those fed the unrefined oils, in the distribution of label within the main lipid classes, indicate that more than one factor is involved in the alterations caused by these oils.     

Influence of dietary fats on weight gain in albino rats

Carbon-chain length and degree of saturation of dietary fat may influence weight gain. To examine this hypothesis we randomly allotted 100 male, 30-day old, albino rats to each of four groups. Each group was fed, ad libitum, a diet containing, as the only source of fat, either lard (L) or safflower oil (SO) (representing saturated and polyunsaturated fat respectively) or groundnut oil (GO) or coconut oil (CO) (representing long-chain and medium-chain triglycerides respectively). At the end of 90 days it was found that rats fed SO consumed more food than those fed L enriched diet (P < 0.001) but the weight gain was similar in the two groups. Similarly rats fed GO-containing diet ate more than those fed diet containing CO (P < 0.001), yet weight gain was similar. Thus it appears that carbon-chain length and degree of saturation of dietary fat does not influence weight gain in rats fed an ad libitum diet.     

A 24-month dietary carcinogenicity study of DAG (diacylglycerol) in rats.

Toxicologic and carcinogenic effects of DAG (diacylglycerol) oil, administered in diet for 24 months to Crl:CD((R))(SD)-IGS BR rats, were evaluated using diet-restricted and ad libitum-fed groups. All dietary fat (consistently 5.5%) was provided by DAG and/or the control article, TG (triacylglycerol) oil. Dietary concentrations (% DAG/% TG) were 0%/5.5%, 1%/4.5%, 2.75%/2.75% and 5.5%/0%. Separate groups were fed the 0%/5.5% and 5.5%/0% diets ad libitum. Another group received the standard rodent diet (fat content 4.5%) on the restricted feeding regimen. Clinical condition, ophthalmic findings, palpable mass occurrence, body composition, clinical pathology parameters and incidence of neoplastic lesions were unaffected by DAG in comparison to TG. Groups fed the 5.5% (DAG and/or TG) fat diet when compared to the 4.5% fat diet group displayed lower survival, higher body weights, organ weights, percent body fat, higher fat-related serum chemistry parameters, incidence of microscopic changes in the heart, kidneys, liver, bone marrow, spleen, and incidences of pituitary and mammary gland neoplasms. Parameters more affected in all the ad libitum groups than in the restricted diet groups (regardless of test article) fed the same diet included survival, body weights, body fat, fat-related serum chemistry parameters, and incidences of heart, kidney and liver microscopic changes. However, the DAG and TG ad libitum-fed groups were not different from one another. Thus, DAG-treated animals had no higher risk of carcinogenic effects than rats fed on similar feeding regimens with a diet in which all dietary fat came from TG.     

Effect of feeding Cuminum cyminum fruits, Thymus vulgaris leaves or their mixture to rats

Cuminum cyminum fruits and T. vulgaris leaves were fed to male Wistar rats at 2% or 10% of standard diet for 6 w. A mixture (5% +5%) of the 2 plants was also fed to rats for a similar period. Diets containing 2% C. cyminum fruits, 2% or 10% T. vulgaris leaves were not toxic to rats. Impairment of growth and enterohepatonephropathy were observed in the rats fed a diet containing 10% C. cyminum fruits. These changes were also seen in the rats fed the mixture of the 2 plants and were accompanied by leukopenia, anemia and increases in serum AST activity and urea and by decreased total protein and albumin levels.     

Antioxidant property of Nigella sativa (black cumin) and Syzygium aromaticum (clove) in rats during aflatoxicosis

Aflatoxins, a group of closely related, extremely toxic mycotoxins produced by Aspergillus flavus and A. parasiticus, can occur as natural contaminants of foods and feeds. Aflatoxins have been shown to be hepatotoxic, carcinogenic, mutagenic and teratogenic to different animal species. Nigella sativa (black cumin) and Syzygium aromaticum (clove) oil are used for the treatment of inflammatory diseases and have antioxidant properties. The aim of this study was to investigate the ability of these volatile oils to scavenge free radicals generated during aflatoxicosis. Sixty male rats were divided into six treatment groups, including a control group, and the groups were treated for 30 days with Nigella sativa and Syzygium aromaticum oils with or without aflatoxin. Blood samples were collected at the end of the experimental period for haematological and biochemical analysis. The results indicated that exposure to aflatoxins resulted in haematological and biochemical changes typical for aflatoxicosis. Treatment with Nigella sativa and Syzygium aromaticum oil of rats fed an aflatoxin-contaminated diet resulted in significant protection against aflatoxicosis. Moreover, Nigella sativa oil was found to be more effective than Syzygium aromaticum oil in restoring the parameters that were altered by aflatoxin in rats.     

Rapeseed oil ingestion and exacerbation of hypertension-related conditions in stroke prone spontaneously hypertensive rats

Two groups of 20 stroke prone spontaneously hypertensive rats (SHRSP) at 5 weeks old were fed a diet containing 10 w/w% rapeseed (canola) oil or soybean oil as the only dietary fat, and given drinking water containing 1% NaCl. Life span of the canola oil group (62+/-2 days) was shorter than that of the soybean oil group (68+/-3 days). Stroke-related symptoms were observed in every animal, but the onset of those in the canola oil group, at 47+/-1 days after starting the administration was earlier than that in the soybean oil group, 52+/-2 days. Incidence of cerebral hemorrhage was similar in these groups, and no differences were found between lesions of organs in the groups. In another experiment, two groups of ten SHRSP at 5 weeks of age were fed the defatted diet and given canola oil or soybean oil by gavage at 10 w/w% of consumed food for 4 weeks without NaCl loading. After the 4-week administration, mean systolic blood pressure in the canola oil group and the soybean oil group were 233+/-2 and 223+/-0.3 mmHg, respectively. Phytosterol levels in both plasma and erythrocyte membranes reflected those contained in the oils ingested. Na(+), K(+)-ATPase activities in the brain, heart and kidney were enhanced in the canola oil group. These results indicate that promotion of hypertension-related deterioration in organs is likely to have relevance to the short life span in the canola oil group. Enhanced Na(+), K(+)-ATPase activity by phytosterols in the oil ingested may play a role in these changes.     

罗格列酮联合二甲双胍对肥胖大鼠脂肪肝的防治作用

目的 观察罗格列酮联合二甲双胍对大鼠非酒精性脂肪肝(NAFID)的防治作用.方法 42只SD大鼠随机分为三组,C组给予正常饮食作为空白对照;A、B组给予高脂饮食12周,A组在高脂饮食同时给予罗格列酮和二甲双胍治疗.12周后处死大鼠,称量大鼠体重和肝脏湿重,检测血糖、血脂、肝功能,并行肝组织病理学检查和肝脏脂肪测定.结果 B组体重、肝湿重、肝指数(肝湿重/体重×100%)均升高(P<0.01);A组肝湿重、肝指数低于B组(P<0.01).B组血糖较C组增加(P<0.05);B组存在脂代谢紊乱,A组脂代谢紊乱明显改善.B组有程度不同肝细胞脂肪变性;脂变程度以中、重度为主;A组肝细胞脂肪变性明显轻于B组(P<0.01);A组肝脏甘油三酯含量明显低于B组(P<0.01).结论 罗格列酮联合二甲双胍可明显改善NAFLD大鼠的血脂紊乱和肝脏脂肪变性.     

A 91-day feeding study in rats with caprenin

Caprenin, a randomized triglyceride primarily comprising caprylic (C8:0), capric (C10:0), and behenic (C22:0) acids, was administered in a semi-purified diet to weanling Sprague-Dawley rats (25/sex/group) at dose levels of 5.23, 10.23 or 15.00% (w/w) for 91 days. Corn oil was added at 8.96, 5.91 and 3.00%, respectively, to provide essential fatty acids and digestible fat calories. Corn oil alone (12.14%) and a blend of medium-chain triglyceride (MCT) oil plus corn oil (11.21 and 3.13%, respectively) served as controls. All diets were formulated to provide about 4000 kcal/kg of diet and 26.8% of digestible calories from fat by assuming that corn oil, MCT oil, and caprenin provided 9, 7 and 5 kcal/g, respectively. Survival, clinical signs, body weight, feed consumption, feed efficiency, organ weights, organ-to-body-weight ratios, organ-to-brain-weight ratios, haematological values and clinical chemistry parameters were evaluated in all groups. Histopathology of a full complement of tissues was evaluated in the corn oil and MCT oil control groups as well as the high-dose caprenin group. Additional rats (n = 5/sex/group) were included in the study to determine whether there was marked storage of C22:0 in heart, liver or perirenal fat at the end of the 91-day feeding period. No significant differences in body weight gain were measured with the balanced caloric diets, although feed conversion efficiency was reduced in the high-dose caprenin group. No adverse effects from the ingestion of caprenin were detected, nor were significant amounts of C22:0 present in the fat extracted from the selected fat depot sites. These results establish a no-observable-adverse-effect level (NOAEL) of more than 15% (w/w) caprenin in the diet (or more than 83% of total dietary fat), which is equal to a mean exposure level of more than 13.2 g/kg/day for male rats and more than 14.6 g/kg/day for female rats.     

The effect of avocado oils on some liver characteristics in growing rats

The effects of various avocado oils on some liver characteristics were studied in growing rats. The rats were fed diets containing 10% (w/w) avocado oil for 4 wk. In comparison with rats fed refined oil obtained from cored fruit by centrifugal separation, rats fed unrefined avocado oil obtained by solvent extraction from the intact fruit, or refined avocado oil containing avocado-seed oil, showed significant growth inhibition, an increase in the amount of hepatic lipids (identified as steatosis by histopathological examination), and a decrease in levels of triglycerides in blood. Rats fed the refined oil containing unsaponifiable material prepared from unrefined oil from the intact fruit showed similar responses. Fatty livers were not induced by feeding rats unrefined avocado oil obtained from intact fruit by centrifugal separation, although a significant decrease in blood triglycerides was observed. There were no significant differences between groups in serum total protein, albumin or bilirubin content or in alanine aminotransferase activity. However, serum alkaline phosphatase activity was increased in rats fed the seed oil, the unrefined solvent-extracted oil from intact fruit, or the unsaponifiables, and aspartate aminotransferase activity was significantly increased in the group fed avocado-seed oil. These data suggest that consumption of avocado oil extracted from intact fruit may cause changes in liver metabolism.     

Effects of conjugated linoleic acid supplementation on blood lipids and adiposity of rats fed diets rich in saturated versus unsaturated fat

Conjugated linoleic acid (CLA) may decrease adiposity and improve blood lipid profiles under some conditions. The goal of this study was to determine the effects of CLA supplementation on blood lipid profiles and adiposity of rats fed a diet containing a primarily saturated fat versus a diet containing a primarily unsaturated fat. Twenty-eight male Sprague-Dawley rats were randomly assigned to one of four diets containing coconut oil, coconut oil with CLA, corn oil or corn oil with CLA. After 28 days, blood was collected and serum concentrations of total cholesterol (TC), HDL-cholesterol (HDL-C), and triacylglycerols (TG) were assessed. Food intake, body weights, and epididymal fat pads were measured. No significant differences (p>0.05) were noted among groups for amount of food consumed, weight gained, food efficiency ratio or serum TG concentrations. TC concentrations were lower (p<0.05) in the CLA-supplemented rats that were fed coconut oil but not those consuming corn oil. Serum HDL-C was lower (p<0.05) in rats consuming corn oil but was not significantly different (p>0.05) for CLA supplemented groups. Epididymal fat pads weighed significantly more (p<0.05) in the coconut oil fed group compared to the corn oil fed group, but there was no significant difference (p>0.05) between the corn oil and coconut oil + CLA group. Overall, this study suggests that CLA is more beneficial for control of blood lipids and adiposity when supplemented to a diet rich in saturated versus unsaturated fat.     

Safety assessment of heated diacylglycerol oil: Subchronic toxicity study in rats

Diacylglycerol oil is an edible oil with similar taste and usability characteristics as conventional edible oil rich in triacylglycerol oil. The objective of the present study was to evaluate potential adverse effects of heated diacylglycerol and triacylglycerol oil in rats following subchronic administration. The heated diacylglycerol and triacylglycerol oils were prepared separately following deep frying potato slices at 180 degrees C for 8h per day for three days. Sprague Dawley rats were fed diets containing different ratios (concentrations) of heated to unheated diacylglycerol oil. The ratio of heated to unheated diacylglycerol was as follows: 0%/5.5% (control-1; Group 1), 1.0%/4.5% (Group 2), 2.75%/2.75% (Group 3), and 5.5%/0% (Group 4). Two additional groups received the feed containing 5.5% of unheated or 5.5% of heated triacylglycerol oil. Compared to the unheated oils, feeding of heated diacylglycerol or triacylglycerol oil did not reveal any toxicologically significant changes in clinical observation, body weights, body weight gains, feed consumption, ophthalmic examinations, functional observational battery and motor activity, clinical pathology evaluations and organ weights. Similarly, terminal necropsy did not reveal treatment-related gross or histopathology findings. Based on the results of this subchronic study, the no-observed-effect levels (NOELs) of heated diacylglycerol or triacylglycerol oil were 5.5%, the highest levels tested. The mean dietary exposure levels at the highest dose for the heated diacylglycerol and triacylglycerol oil for male and female rats ranged from 3,178 to 4,120 mg/kg/day.     

Biological effects of short-term feeding to rats of repeatedly used deep-frying fats in relation to fat mutagen content

The effects of short-term feeding of mutagen containing, heated deep-frying oils on urinary and faecal mutagenicity, plasma clinical biochemical parameters, peroxidative effects and cell proliferative indices in the gastro-intestinal tract were determined in rats. Repeatedly used frying oils [a saturated fatty acid-rich coconut oil (CO) and a polyunsaturated fatty acid (PUFA)-rich (greater than 60% PUFA) vegetable frying oil (PO)] were administered to groups of seven rats at a level of 10% (by weight) in the diet for 4 wk; control groups were fed equal amounts of the unheated oils. Both heated oils showed direct-acting mutagenicity to Salmonella tester strain TA97; heated PO was also mutagenic to strain TA100. Both heated CO and heated PO contained detectable amounts of thiobarbituric acid-reactive substances (TBA-RS). In heated PO, hydroperoxides of linoleic acid were also present. In groups fed heated oils the mutagenicity of urine and faeces to strain TA97 was not found to be increased in comparison with the control groups. Faecal mutagenicity to strain TA100 was also unaffected by consumption of heated oils. Urinary excretion of TA100 mutagens was significantly increased in rats fed heated PO. Plasma alkaline phosphatase activity was clearly raised in rats fed heated PO, in comparison with rats fed unheated oils or heated CO. In addition, other clinical biochemical plasma parameters showed a tendency to be increased in rats fed heated PO, indicating hepatic and renal cellular toxicity. Urinary and faecal excretion of thiobarbituric acid-reactive substances (TBA-RS) were also slightly, but not significantly, increased in rats fed heated PO. Feeding heated CO to rats did not result in increased plasma enzyme activities and excretion of TBA-RS, nor in increased cell proliferation in gastro-intestinal tissues. Cell proliferation of the oesophageal tissues were slightly, but significantly, increased in rats fed heated PO, in comparison with the group fed unheated PO. Tissues of the glandular stomach and colon/rectum did not show significantly enhanced cell proliferation in the group fed heated PO. The results obtained in this study indicated that consumption of heated oils containing TA100 mutagens and oxidation products of linoleic acid produced indications of cellular damage to liver and kidneys, and increased urine mutagenicity, as well as enhanced cell proliferation in the oesophagus.