Changes in blood pressure, vascular reactivity and inflammatory biomarkers following consumption of heated corn oil

Consumption of corn oil for cooking purpose is gaining popularity. The present study examined the effect of heated corn oil on blood pressure and its possible mechanism in experimental rats. Thirty male Sprague-Dawley rats were randomly divided into 5 groups and were fed with the following diets, Group I was fed with basal diet only; whereas group II,III,IV and V were fed with basal diet fortified with 15% (w/w) either fresh, once-heated, five-times-heated or ten-times-heated corn oil, respectively for 16 weeks. Body weight, blood pressure were measured at baseline and weekly interval for 16 weeks. Inflammatory biomarkers which included soluble intracellular adhesion molecules (sICAM), soluble vascular adhesion molecules (sVCAM) and C reactive protein (CRP), were measured at baseline and the end of 16 weeks. The rats were sacrificed and thoracic aorta was taken for measurement of vascular reactivity. There was significant increase in the blood pressure in the groups fed with heated once, five-times (5HCO) and ten-times-heated corn oil (10-HCO) compared to the control. The increase in the blood pressure was associated with an increase in CRP, sICAM and sVCAM, reduction in vasodilatation response to acetylcholine and greater vasoconstriction response to phenylephrine. The results suggest that repeatedly heated corn oil causes elevation in blood pressure, vascular inflammation which impairs vascular reactivity thereby predisposing to hypertension. There is a need to educate people not to consume corn oil in a heated state.

Effects of three biodiesels and a low sulfur diesel in male rats--a pilot 4-week oral study

Because of the accessible and renewable nature of feedstock and the potential for the reduction of harmful combustion emissions and greenhouse gases, biodiesels have received increasing interest as an alternate fuel. Oral exposure to biodiesels is a concern because of contact during refuelling, accidental ingestion and exposure through ground water contamination. Although biodiesels from various feedstock are in use commercially and experimentally, very little is known about their potential adverse effects and no data is available on their potential for ground water contamination. A study was performed on male rats following oral treatment with experimental biodiesels (dissolved in corn oil) derived from canola oil (Bio-C), soy oil (Bio-S) and fish oil (Bio-F), at 500 mg/kg body weight/day, 5 days per week, for 4 weeks. Separate groups of animals were treated with low sulfur diesel (LSD) for comparison purpose, and with corn oil alone to serve as control. The potential for ground water contamination by biodiesels was investigated by the preparation of water-accommodated fractions (WAF) followed by gas chromatographic analysis. WAF from Bio-F and Bio-S was found to have the highest level of dichloromethane extractable materials. Gas chromatographic analysis indicated that the extractable materials from biodiesels contained much higher proportion of C15-C30 materials than LSD. Increased liver weight was observed in animal treated with Bio-C, Bio-S and LSD and decreased thymus weight was found in those treated with Bio-S. Histopathological changes typical of male-rat specific hyaline-droplet nephropathy were detected in kidney tubules of animals treated with LSD, Bio-S and Bio-C. Mild adaptive changes were observed in thyroids of animals treated with LSD, Bio-S and Bio-F. Clinical chemical and biochemical changes were confined to Bio-S and LSD treated rats and included elevation in some hepatic phase-I and phase-II drug metabolizing enzymes and hepatic palmitoyl Co-A oxidase, and elevated urinary concentrations of ascorbic acid and albumin. At the given dose level of 500 mg/kg bw/day, the overall treatment-related effects of biodiesels and LSD are mild, and the severity of the treatment effects may be ranked as: LSD>Bio-S>Bio-C>Bio-F. Considered together with the presence of a higher level of water extractable materials, Bio-S may be more of a concern for potential human health than Bio-C and Bio-F in an oral exposure scenario. Further studies are needed to identify and characterize the constituents contributing to the treatment-related effects specific to these experimental biodiesels.

Effect of rancid corn oil on some onco/suppressor gene expressions in vivo. A short-term study

Autooxidation of polyunsaturated fatty acids (PUFAs) of edible oils results in the formation of fatty acid hydroperoxides that can undergo further chemical transformations to yield a variety of re-arranged and chain-cleavage products. Since the oxidation products of PUFAs have been reported to have cytotoxic and mutagenic effects, the consumption of rancid oils and fats represents a possible health hazard for the population. Storage of corn oil at room temperature and in the refrigerator for a forty-eight month period resulted in two different qualities of oil samples, which were characterized by UV, titrimetric (peroxide value, acid value) and GC-MS methods. Earlier it was demonstrated that the increase of expression of certain oncogenes and tumor suppressor genes is a method of choice for the early detection of carcinogen exposure. Treatment of CBA/Calpha inbred mice with the two oil samples showed significantly increased expression of the Ha-ras gene in all the investigated organs (liver, lung, kidney, thymus and spleen) of the rancid corn oil-treated animals. Expression of the c-myc and the p53 genes was also increased after the rancid corn oil-treatment in all the organs but the thymus of the mice. The results suggest that rancid oils, rich in omega-6 unsaturated fatty acids, could be involved not only in tumor promotion but in initiation as well.

Subchronic toxicity of fish oil concentrates in male and female rats

There are an overwhelming number of reports indicating the beneficial effects of fish oil supplements in human and animal nutrition. The purpose of this study, second in a series, was to evaluate the effects, particularly those that may be harmful, of high-dose, long-term consumption of fish oil concentrates (FOC) using male and female rats. One hundred and twenty male and 120 female rats were gavaged daily with oils and oil mixtures in a volume equal to 0.5% body weight (5 mL/kg/d) for 13 weeks. The administered oils were corn oil, pure menhaden oil (MO), pure MaxEPA fish oil or different mixtures of corn oil with MO. The stability and the homogeneity of the dosing solutions were tested under study conditions. The animals received isocaloric and isonitrogenous diets throughout. Food and pure water were supplied ad libitum. At the end of the in-life phase of the study, the animals were anaesthetized with CO2 and humanely killed by exsanguination. Blood and other tissues were prepared for various clinical, histopathological and laboratory tests. Some beneficial effects of FOC, such as reduction in total serum cholesterol, in rats were confirmed. However, we also observed a significant reduction in absolute amount of serum HDL and a significant increase in relative liver and spleen weights in both sexes with the high dose of FOC. High doses of FOC (5 mL/kg/d) reduced serum iron and vitamin E concentrations. A reduction in osmotic fragility of RBC as well as an increase in RBC deformity were also observed in rats treated with high doses of FOC. These rats showed a significant overall increase in WBC count. We conclude that in rats, subchronic consumption of high levels of FOC can be beneficial but may also be harmful because of induction of clinical abnormalities including increased red cell deformity, increased relative liver and spleen weights, and reduced serum HDL, iron and vitamin E concentrations.

Chronic study of diacylglycerol oil in rats

The objective of the present study was to evaluate the effects of diacylglycerol oil following long-term administration to rats. Diacylglycerol oil is an edible oil with comparable taste and physicochemical properties of several naturally occurring oils. Diacylglycerol oil can be used as a replacement for any generally used edible oil in the home and has been approved for use in cooking oil in Japan. Male and female Sprague-Dawley rats were divided into four groups and fed low-fat (1.7%) basal diets containing an edible oil composed of rapeseed, corn, high linoleic safflower and high oleic safflower oils at 5.3% (control group 1); an edible oil composed of rapeseed and soybean oils at 5.3% (control group 2); diacylglycerol oil at 2.65% plus edible oil composed of rapeseed, corn, high linoleic safflower and high oleic safflower oils at 2.65% (low-dose group); and diacylglycerol oil at 5.3% (high-dose group) for 2 years. Interim sacrifices were conducted at weeks 30 and 77 and the study was terminated following 105 weeks of feeding. No compound-related effects were noted on clinical signs, body weights, food consumption, cumulative survival rates, hematology, blood chemistry, urinalysis, organ weights or on microscopic non-neoplastic changes. Compared to control group 2, but not control group 1, there was a significant increase in the number of high-dose group females with either benign or malignant epithelial mammary gland neoplasms. These changes were not considered biologically significant, because the tumor incidence was not similar in control group 1 and 2, and the neoplastic findings were not dose related. In summary, the two-year chronic rat study revealed no toxicologically significant or treatment-related effects of diacylglycerol oil consumption at levels of up to 5.3% in the diet.

Toxicity of oxidized fats II: tissue levels of lipid peroxides in rats fed a thermally oxidized corn oil diet

Male Wistar albino rats were fed for 21 days on a diet in which fat (12%) was included either as fresh corn oil, malonaldehyde content = 0.11+/-0.05 micro microg/g (control) or thermally oxidized corn oil, malonaldehyde content = 0.20+/-0.03 microg/g (experimental) and the tissue levels of lipid peroxides in six organs-namely, liver, kidney, brain, heart, lungs and testes-were determined. Of the organs studied, significantly (P < 0.1) higher concentrations of lipid peroxides were observed only in the liver and kidney of the experimental rats. In the course of the feeding, the experimental rats showed significantly (P < 0.1) lower gains in body weights as well as higher relative liver weights than the control rats.

Butylated hydroxytoluene prevents hepatic damage induced by food oil

A rapid and reproducible model of fatty liver in rats was developed by injecting corn oil (s.c.). In preliminary experiments, the mortality due to acute ethanol intoxication was significantly higher in this model of acutely fattened animals. Lipid peroxidation is a process that involves free radicals and consumes as substrate unsaturated fatty acids, which are present in great amounts in corn oil. Thus, in this work we explored whether the acute loads of corn oil increased hepatic lipid peroxidation. The three markers of cellular oxidative stress measured in fatty livers from rats injected with corn oil were: the production of thiobarbituric acid-reactive substances (TBARS), liver content of triacylglycerides (TAG), and total glutathione (GSH-GSSG). All were significantly modified. We also studied the effect of butylated hydroxytoluene (BHT), a free radical scavenger frequently used in the food industry to prevent lipid oxidation, and found that it prevented the effect of corn oil on TBARS and TAG but enhanced the depletion of GSH-GSSG caused by the acute administration of large loads of corn oil.

Inhibitory effects of diallyl disulfide or aspirin on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine-induced mammary carcinogenesis in rats

Modifying effects of diallyl disulfide (DAD), aspirin or DL-alpha-difluoromethylornithine (DFMO) on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis in SD rats were investigated. A total of 166 female rats, 6 weeks old, were divided into 8 groups. They were fed a high fat diet throughout the experiment. Starting at 7 weeks of age, groups 1-4 were given PhIP (85 mg/kg body weight in corn oil) by gavage 8 times in 10 days, and groups 5-8 were given corn oil alone. For the beginning 4 weeks, groups 2 and 5 were given DAD at 200 ppm in diet. Similarly groups 3 and 6, and groups 4 and 7 were given aspirin (400 ppm) and DFMO (400 ppm), respectively. Mammary carcinomas were only recognized in groups 1-4 at the termination (25 weeks after the start of experiment). Multiplicity (mean number/rat) of neoplasms in group 2 (PhIP+DAD, 0.90/rat) and group 3 (PhIP+aspirin, 1.37/rat) was significantly smaller than that in group 1 (PhIP alone, 2.45/ rat) (P < 0.005 and P < 0.05, respectively). These results indicate that dietary intake of DAD or aspirin during the time corresponding to initiation phase has chemopreventive potential on PhIP-induced mammary carcinogenesis in rats.

Aortic antioxidant defense and lipid peroxidation in rabbits fed diets supplemented with different animal and plant fats

OBJECTIVE

To test the hypothesis that dietary fats, depending on the fat source, may modulate aortic lipid peroxidation and antioxidant protection.

METHODS

Rabbits were fed a low fat (LF, 2 g/100 g corn oil) diet or LF enriched with 16 g/100 g (w/w) of corn oil (CO), corn oil plus cholesterol (23.5 mg/100 g diet, CO + C), bovine milk fat (MF), chicken fat (CF), beef tallow (BT) or lard (L). After a 30-day feeding period, aortic lipid peroxidation, as well as antioxidant enzymes and vitamin E were measured.

RESULTS

In rabbits fed CO or L, aortic TBARS (a marker of lipid peroxidation) and total glutathione concentrations were greater but vitamin E levels were lower compared with the LF treatment. Moreover, in rabbits fed CO, elevated activities of glutathione peroxidase and glutathione reductase but lowered activity of superoxide dismutase were observed. In rabbits fed the remaining high fat diets, including the CO + C diet, aortic lipid peroxidation and antioxidant activities/levels did not differ from those fed LF. Feeding rabbits high-fat diets for 30 days did not induce aortic lipid deposition.

CONCLUSIONS

The present results indicate CO, and possibly L, as the fat sources which significantly increase aortic oxidative stress. Because long-term disturbances in redox status may be implicated in atherogenesis, excessive dietary intake of CO or L may significantly contribute to the injury of the vessel wall.

Effect of amount and types of dietary fat on intestinal bacterial 7 alpha-dehydroxylase and phosphatidylinositol-specific phospholipase C and colonic mucosal diacylglycerol kinase and PKC activities during stages of colon tumor promotion

It is evident from many studies that the effect of dietary fat on colon tumor promotion depends not only on the amount of fat but especially on fatty acid composition. Animal model studies have shown that diets which are high in omega-6 fatty acids increase colon tumor promotion, whereas diets rich in omega-3 fatty acids have no such enhancing effect. The mechanisms by which the high fat content of the diet promotes colon carcinogenesis may include the production of secondary bile acids in the colon and the modulation of colonic luminal bacterial 7 alpha-dehydroxylase that is involved in generating secondary bile acids, phosphatidylinositol-specific phospholipase C (PI-PLC), and mucosal PI-PLC, as well as diacylglycerol (DAG) kinase and protein kinase C (PKC). In the present study, we investigated the effect of high-fat diets that are rich in omega-3 and omega-6 fatty acids on cecal bacterial 7 alpha-dehydroxylase and PI-PLC, fecal secondary bile acids, and colonic mucosal DAG kinase and PKC activities during different stages of colon carcinogenesis in male F344 rats. At 5 weeks of age, groups of animals were fed a low-fat diet containing 5% corn oil (LFCO). Beginning at 7 weeks of age, all animals, except those intended as vehicle controls, received azoxymethane (AOM) s.c. once weekly for 2 weeks at a dose rate of 15 mg/kg body weight. Vehicle-treated groups received s.c. injections of normal saline. One day after the second AOM or saline treatment, the experimental groups of animals were transferred to a high-fat diet containing 23.5% corn oil (HFCO) or 20.5% fish oil + 3% corn oil (HFFO). One group continued on the LFCO diet. Animals were sacrificed at weeks 1, 12, and 36 after the AOM or saline treatment. Colonic mucosa were harvested at weeks 1, 12, or 36, and the colonic tumor tissues were examined for PKC and DAG kinase activities. Contents of the cecum were analyzed for bacterial 7 alpha-dehydroxylase and PI-PLC activities. Stool samples collected at week 12 were analyzed for bile acids. High corn oil content of the diet significantly increased the cecal bacterial 7 alpha-dehydroxylase and PI-PLC activities as compared to the diets with high fish oil or low corn oil content. Animals fed the HFCO diet excreted higher levels of secondary bile acids, such as deoxycholic acid and lithocholic acid, than those fed the LFCO or HFFO diets. Carcinogen treatment significantly enhanced the activities of DAG kinase and total membrane PKC activities in colonic mucosa compared to saline treatment in all dietary groups. Animals treated with saline or AOM and fed HFCO showed increased levels of DAG kinase and membrane PKC activities in the colonic mucosa when compared to LFCO and HFFO groups. DAG kinase and membrane PKC activities were higher in colon tumors than in the surrounding colonic mucosa, and also increased levels of these enzyme activities were found in the HFCO diet group. These results indicate that the modifying effect of dietary fat on colonic bacterial enzymes, secondary bile acids, colonic mucosal and tumor DAG kinase, and PKC that may play a role in colon carcinogenesis depends on the types and amount of fat given. The colon tumor-enhancing effect of a HFCO diet in contrast to the high dietary fish oil may be, in part, explained on the basis of its modulating effect on these bacterial and colonic mucosal enzymes and colonic secondary bile acids relevant to colon tumor promotion.

Dietary effects of corn oil, oleic acid, perilla oil, and evening [corrected] primrose oil on plasma and hepatic lipid level and atherosclerosis in Japanese quail

To compare the atherogenecity of different fats and oils, a total of forty, 40-day-old male Japanese quails were fed one of the following diets for three months: basal diet (control), a diet-containing 15% corn oil (CO) and 2% cholesterol (CH), a diet-containing 15% oleic acid (OL) and 2% CH, a diet-containing 15% perilla oil (PE) and 2% CH, a diet-containing 15% evening [corrected] primrose oil (PR) and 2% CH. A higher plasma cholesterol concentration was found in the birds in the CO and OL groups, whereas the PE and PR groups showed a much lower level of plasma cholesterol than the CO and OL groups. In proportion to the increased plasma cholesterol, both CO and OL groups showed narrowing of the lumen of the ascending aorta and its large branches due to marked lipid-rich intimal thickening. Ultrastructural changes in the ascending aorta and its large branches were correlated with the degree of intimal thickening. The major foam cell types were macrophages and fibroblastic cells. The PE and PR groups showed the fewest lipid-rich intimal thickening lesions in their ascending aorta and its large branches. These findings suggest that the alpha-linolenic acid contained in perilla oil is less atherogenic than oleic and linoleic acid, and gamma-linolenic acid contained in evening [corrected] primrose oil has a tendency to decrease the plasma lipid level.

Alterations in nuclear ploidy and cell phase distribution of rat liver cells in experimental alcoholic liver disease: relationship to antioxidant enzyme gene expression

The ability of a cell to withstand oxidative stress has been hypothesized to be related to its ploidy status. We used the intragastric feeding rat model for alcoholic liver disease to evaluate the relationship between severity of liver injury, antioxidant mRNA levels, and DNA ploidy of liver cells. Rats were fed ethanol with different dietary fats (saturated fat, corn oil, and fish oil); pair-fed control animals received isocaloric amounts of dextrose. All animals were euthanized at 1 month and had evaluation of pathologic changes in the liver, DNA content by flow cytometry, and mRNA levels for catalase and glutathione peroxidase. The fish oil-ethanol group exhibited the most severe pathology, the corn oil-ethanol group had intermediate pathologic changes, and no pathologic changes were seen in the saturated fat-ethanol and dextrose-fed controls. Flow cytometric analysis of propidium iodide-stained nuclei revealed that saturated fat-dextrose and corn oil-dextrose groups had about 65% of cells with (diploid) G1 DNA content and about 30% of cells with tetraploid (4C) nuclei. The fish oil-dextrose had a significantly higher (p < 0.001) number of 4C cells (67.4 +/- 2.1%) compared to the other two dextrose-fed groups. In the animals showing pathologic liver injury, there was a higher percentage of cells with hypertetraploid nuclei. The highest percentage of these hypertetraploid cells was seen in the fish oil-ethanol group. Catalase and glutathione peroxidase mRNA levels correlated significantly with polyploidy. A significant correlation was seen between the number of cells in the greater than G2 + M phase and glutathione peroxidase mRNA levels (r = 0.91, p < 0.01) and catalase mRNA. The different slopes of correlation analysis between catalase mRNA and dietary fats show that the degree of saturation of fatty acids may influence catalase mRNA expression in cells with different ploidy states. We propose that polyploidization of liver cell nuclei may serve as a defense mechanism against ethanol-induced hepatotoxicity. This defense mechanism may also, in part, account for the antiregenerative effect of ethanol on hepatocytes.

Effects of a single dose of the cytochrome P450 inducer, beta-naphthoflavone, on hepatic and renal covalent DNA modifications (I-compounds)

I-compounds are age-dependent covalent DNA modifications, which occur in rodent tissues without known carcinogen exposure. A number of studies from our laboratory indicate that I-compounds may serve as biomarkers of carcinogenesis. Recently, we demonstrated significant lowering of liver I-compound levels in rats that were exposed to different cytochrome P450 inducers. In order to gain further mechanistic insights into the possible relationship between P450 induction and I-compound reduction, female Sprague-Dawley rats were administered a single dose of the CYP1A1 inducer, beta-naphthoflavone (BNF) (80 mg/kg), in corn oil (CO) (2 ml/kg) or CO only (2 ml/kg) as vehicle control. Liver and kidney microsomal P450 contents and P450-related enzyme activities and DNA I-compounds were determined at 4, 24, and 48 h after treatment. Liver and kidney I-compounds were analyzed by nuclease P1-enhanced 32P-postlabeling. DNA synthesis was determined by measuring [3H]methylthymidine incorporation. Liver and kidney microsomal P450 contents were elevated by BNF at 24 and 48 h. Ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MROD) were significantly elevated at all time points, with the former displaying a much higher extent of induction. BNF treatment resulted in significant diminution of the levels of several individual and total I-compounds in liver at 48 h, but few effects were seen at the earlier time-points. Kidney I-compounds were also markedly affected by BNF at 48 h, albeit to a lesser extent than in liver. In both tissues, P450 induction preceded I-compound reduction. Taken together, the results of this investigation demonstrate significant diminution of I-compound levels by a single dose of BNF, a CYP1A1 inducer, in a time-dependent manner, suggesting the participation of a specific biochemical process, possibly involving CYP1A1, in the metabolic regulation of these endogenous DNA adducts.

Toward an animal model of chronic pancreatitis. Pancreatobiliary secretion in hamsters on long-term treatment with chemical inducers of cytochromes P450

There is currently no reproducible model of the painful and lithogenic disease, chronic pancreatitis. Its biphasic evolution, from acinar cell hyperplasia and hyperactivity toward effacement of enzyme as well as bicarbonate secretory parenchyma, would be rationalized if it was linked to induction of cytochrome P450 mono-oxygenases (CYP): the increased oxidant load from long-term CYP induction eventually erodes micronutrient antioxidant defenses to injure cells. This philosophy would also rationalize the reported hepatobiliary aberrations associated with the human disease, including increases in free radical oxidation products in bile. Accordingly, pancreatic and biliary secretions were studied in Syrian golden hamsters that were reared for 6 mo on low or high (16% corn oil) fat diets that were supplemented with a prototype inducer of CYP2 (200 ppm phenobarbitone) or CYP1 (100 ppm beta naphthoflavone) enzyme families, with or without a putative enzyme inhibitor (400 ppm cimetidine). The drugs did not alter the reduction in flow rate or bicarbonate concentration of pancreatic juice caused by the high fat diet alone, but, in contrast, evoked pancreatic protein hypersecretion in a number of animals. beta naphthoflavone, but not phenobarbitone, augmented the output of biliary lipid peroxidation products irrespective of dietary fat content, and cimetidine cotreatment with either inducer did the same. We conclude: (1) that drug modifiers of CYP magnify the deleterious pancreatobiliary effects of corn oil-enriched diets and draw them closer to those found in human chronic pancreatitis; (2) that these functional derangements are accompanied by pancreatic lipoatrophy; and (3) that long-term CYP induction does not, of its own, cause fibrosis or the ductal abnormalities that generally accompany loss of pancreatic acinar cells in the human disease and, also in contrast, the changes that are caused appear to be painless.

The combined effects of dietary fat and estrogen on survival, 7,12-dimethylbenz(a)anthracene-induced breast cancer and prolactin metabolism in rats

The relationships between dietary fat concentration (10 or 40% of energy), fat source (corn oil or beef tallow) and estrogen (control, ovariectomy or ovariectomy with estrogen replacement) to 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast carcinogenesis and survival in rats were studied in a 2 x 2 x 3 factorial experiment. Female Sprague-Dawley rats given DMBA (2.5 mg/100 g body wt, intragastric) at 55 d of age were randomly allocated to three groups 48 h later: sham ovariectomy (control), ovariectomy (OVX) or ovariectomy with a subcutaneous estrogen implant (OVX+E). Each group was subdivided into dietary groups fed 10 and 40% of energy as corn oil or beef tallow for 70 wk. OVX+E rats exhibited serum estrogen concentrations in excess of physiologic values. Survival at 70 wk for the 3 hormonal groups was control 51%, OVX 67% and OVX+E 13%. Mortality in controls was doubled by feeding a high fat diet; no diet effect was detected in OVX or OVX+E rats. Palpable tumors developed in 74, 14 and 60% of control, OVX and OVX+E rats, respectively. High fat diets approximately doubled the hazard of developing a palpable tumor. Adenocarcinoma prevalence was 58, 12 and 63% in control, OVX and OVX+E rats, respectively. The odds of having any tumor, an adenocarcinoma or an adenoma were multiplied by 3.6, 2.8 and 2.3, respectively, for rats fed high vs. low fat. Additional studies showed that diet had no effect on serum prolactin or estrogen concentrations or metabolism and clearance of intravenously administered radiolabeled prolactin. We demonstrated that high dietary fat concentration enhances breast carcinogenesis independently of cyclic ovarian function, although the presence of estrogen may be a prerequisite for significant dietary modulation. The effect of fat on breast cancer is not mediated by major changes in systemic prolactin metabolism.

Dose-dependent vehicle differences in the acute toxicity of bromodichloromethane

Bromodichloromethane (BDCM) is a disinfection by-product of drinking water chlorination and is the second most common trihalomethane (THM) in finished drinking water. THMs have generally been administered to experimental animals in corn oil, rather than drinking water, which can influence the site and magnitude of toxicity. To examine the effects of gavage vehicle on the acute renal and hepatic toxicity of orally administered BDCM, 95-day-old male F344 rats were given single doses of 0, 200, or 400 mg BDCM/kg in corn oil or an aqueous 10% Emulphor solution. Activities of serum hepatoxicity indicators were significantly greater 48 hr after administration of 400 mg BDCM/kg in corn oil compared to the aqueous vehicle, but delivery of the low dose in either dosing vehicle had little effect on serum enzymes. In contrast, significant elevations in urinary renal toxicity indicators were noted at 200 and 400 mg BDCM/kg in both vehicles after 24 hr, indicating that the kidney is more sensitive to low doses of BDCM than the liver. Significantly greater increases were observed in urinary indicators after delivery of 200 mg BDCM/kg in 10% Emulphor compared to corn oil. However, administration of the high dose in corn oil resulted in greater nephrotoxicity than in the aqueous vehicle. Significant interactions between vehicle of administration and BDCM dose observed for both urinary and serum parameters further indicate that vehicle differences noted in BDCM acute toxicity are dose dependent. This observation may be due to pharmacokinetic differences in gastrointestinal rates of absorption of BDCM from corn oil as compared to an aqueous solution.

Indomethacin-induced gastrointestinal ulcers in rats: effects of dietary fatty acids and endotoxin

The purpose of this study was to determine how dietary n-3 and n-6 polyunsaturated fatty acids (PUFA) affected the gastrointestinal response to lipopolysaccharide (LPS) and indomethacin (INDO) in the rat. Rats were fed diets containing 12.5% linseed oil (LO-enriched in short-chain n-3 PUFA) or corn oil (CO-enriched in n-6 PUFA). After 30 days on the diets, rats were given one of three treatments 1:10 mg/kg O55:B5 Escherichia coli LPS intraperitoneally (i.p.), 2:25 mg/kg INDO subcutaneously (s.c.), 3: a combination of 10 mg/kg i.p. LPS and 25 mg/kg (s.c.) INDO given 30 min before LPS. 20 h after challenge, rats were given an intravenous injection of Monastral Blue B to stain ulcer areas in the gastrointestinal tract. Lipopolysaccharide did not result in any Monastral Blue B vascular leakage in the gastrointestinal tract. Rats on the LO diet had significantly increased stomach and intestinal ulcers compared to CO fed rats. When rats were challenged with LPS and INDO, the LPS almost completely eliminated small intestinal ulcers, but enhanced ulcer development in the stomach.

Influence of dietary omega-6, -3 fatty acid sources on the initiation and promotion stages of photocarcinogenesis

To determine the segment along the carcinogenic continuum at which dietary lipid exerts its principal effect, six groups of 35 Skh-HR-1 hairless mice were placed on defined isocaloric diets containing either 0.75%, 12% corn oil or 12% menhaden oil as sources of omega-6 or omega-3 fatty acids, respectively. All animals received an 11 week course of UV-radiation from fluorescent sunlamps. Upon termination of UV, diets of some groups were crossed-over to either low fat, high fat, omega-6 or omega-3 fatty acid sources. The first tumor appeared at week 14. Life-table analysis of the tumor incidence curves and Wilcoxon tests of tumor multiplicity provided evidence that high corn oil diets significantly (P less than 0.01) enhance carcinogenic expression; that tumor enhancement by the omega-6 fatty acid source occurs during the post-initiation, or promotion, stage; that replacement with a low corn oil diet after UV-initiation will negate the exacerbating effect of high corn oil; and that an omega-3 fatty acid source inhibits UV-carcinogenesis even at high dietary levels, although not during the post-initiation stage.

Effects of corn oil, time-related changes, and inter-laboratory variability on tumor occurrence in control Fischer 344 (F344/N) rats

Survival, body weight, and site-specific tumor rates in untreated, corn oil gavage, and water gavage control Fischer 344 (F344/N) rats from 88 National Toxicology Program (NTP) long term carcinogenicity studies were evaluated to determine which factors were primarily responsible for inter-study variability. For male rats, previously-reported decreases in leukemia and increases in body weight, survival, and pancreatic acinar cell tumors attributable to corn oil gavage were confirmed. Corn oil did not appear to affect tumor rates in female rats. The gavage technique per se did not appear to influence tumor rates in rats of either sex. Previously reported time-related increases in certain site-specific neoplasia in control rats appeared to have stabilized in recent years, but control tumor rates are still much greater than those seen a decade ago. More recent studies continue to show increasing rates of leukemia and mammary gland tumors and decreasing survival. Female rats also continue to show time-related increases in maximum mean body weight. Inter-laboratory variability in body weight and in the rates of a number of site-specific neoplasms were also significant. High mean body weights in control groups were found to be associated with increased rates of mammary and pituitary tumors. Our evaluation supports the view that if historical control data are to be utilized in the interpretation of experimental results, primary emphasis should be given to lab and route of administration-specific tumor rates for studies that are contemporary to the study under evaluation. It also suggests that certain experimental design changes (e.g., dietary modifications) may be needed to reduce tumor rates and to increase survival.

Effects of a long-chain fatty amine on mammary carcinogenesis induced in female Sprague-Dawley rats by DMBA

Reports that protein kinase C is inhibited by sphingosine and other long-chain amines and the suggestion that promotion of mammary carcinogenesis by dietary fat is mediated by protein kinase C prompted us to investigate the effects of a long-chain amine, 1-octadecylamine, on mammary carcinogenesis induced by 7,12-dimethylbenz[a]anthracene in rats fed a high-fat diet. Rats fed the amine sulfate at a level of 0.01% in a semipurified diet containing 20% corn oil developed more tumors than those fed the high-fat diet alone, although body weight gain was inhibited slightly. Rats fed the amine sulfate at 0.1% of the diet developed very few tumors compared with those fed either the high-fat diet or a low-fat diet containing 5% corn oil. At the higher level, the C18 amine also caused a marked inhibition of body weight gain.

Effect of dietary fat on human breast cancer growth and lung metastasis in nude mice

Results from epidemiological studies have generally indicated an association of dietary saturated animal fats with human breast cancer risk. Some studies, however, have suggested a similar association for some polyunsaturated vegetable fats shown to promote both rodent mammary carcinogenesis and metastasis. This study was performed to evaluate the effects of corn oil on growth and metastasis of MDA-MB-435 human breast cancer cells, which have a propensity for metastasis. Corn oil is rich in the omega-6 fatty acid linoleic acid. Fifty-eight female athymic nude mice (NCr-nu/nu) were fed a high-fat diet (23% wt/wt corn oil; 12% linoleic acid) or a low-fat diet (5% wt/wt corn oil; 2.7% linoleic acid). Seven days after diets were started, tumor cells (1 x 10(6) were injected into a mammary fat pad. The time to appearance of solid tumors and the tumor size were recorded. After 15 weeks, the study was terminated, and autopsies were performed to determine the weight of the primary tumor and the extent of metastasis. The latent interval for tumor appearance in the animals fed the high-fat diet was shorter than that in the low-fat diet group, and the tumor growth rate in the high-fat diet group showed a small but statistically significant increase compared with the low-fat diet group. Primary tumors developed in 27 of the 29 mice on the high-fat diet and in 21 of the 29 on the low-fat diet. Of the mice with palpable primary tumors, 18 of 27 in the high-fat diet group and eight of 21 in the low-fat diet group had macroscopic lung metastases. The extent of metastasis in the high-fat diet group was independent of the primary tumor weight, but only those in the low-fat diet group with primary tumors weighing more than 2 g developed metastases. These results suggest that a high-fat diet rich in omega-6 polyunsaturated fatty acid can enhance metastasis of human breast cancer cells in this mouse model. The findings support the need for further study of the relationship between dietary polyunsaturated fats and breast cancer risk and for experiments to determine the effect on metastasis of only a 50% difference in fat intake--the dietary goal of the proposed clinical trials of low-fat dietary intervention in breast cancer patients.

Relative sensitivity of 32P-postlabelling of DNA and the autoradiographic UDS assay in the liver of mice exposed to 2-acetylaminofluorene (2AAF)

In contrast to earlier studies conducted at lower dose levels, 2AAF is shown to induce a positive UDS response in the liver of mice dosed orally at dose levels between 500 and 1000 mg/kg. Similarly exposed mice had low levels of 2AAF-related hepatic DNA adducts at dose levels in the range 10-1000 mg/kg 2AAF, as determined by 32P-postlabelling analysis. It is concluded that the attenuated UDS response observed in the mouse liver, as compared to the rat liver, is due primarily to metabolic differences between these two species, coupled to a reduced capacity for UDS in the mouse liver for a given level of total 2AAF-related adducts per unit of DNA. These observations are compared and contrasted with identical studies conducted in the rat and reported in the preceding paper (Gallagher et al., 1991).

Relative sensitivity of 32P-postlabelling of DNA and the autoradiographic UDS assay in the liver of rats exposed to 2-acetylaminofluorene (2AAF)

Groups of male Alderley Park rats were dosed concomitantly with 2-acetylaminofluorene (2AAF) by gavage at doses between 0.01 mg/kg and 40 mg/kg, and livers sampled 2-72 h later. The liver of one group of animals was perfused to yield hepatocytes which were assayed in vitro for unscheduled DNA synthesis (UDS) via incorporation of tritiated thymidine and autoradiography. DNA was extracted from the livers of the other group and DNA adduct levels determined using the 32P-postlabelling technique. The major C-8 2-aminofluorene/guanosine adduct and 3 minor adducts were quantitated, enabling the relative sensitivity of the 2 techniques to be compared. A dose- and time-related UDS response was observed, which, at the most sensitive time-point (12 h) enabled DNA repair to be discerned at a dose level of 0.1-1 mg/kg of 2AAF, a response classified as formally positive at 5 mg/kg 2AAF. Only the C-8 adduct, as determined by 32P-postlabelling, was discernible at 0.01 mg/kg of 2AAF, although other adducts were visible on autoradiograms at higher dose levels. It is concluded that as part of a well-defined dose response, UDS can be discerned with confidence for doses of 2AAF between approximately 0.1 and 5 mg/kg, and DNA adducts for doses of 2AAF between approximately 0.01 and 1 mg/kg. Discernible UDS for 2AAF in the rat liver is apparent at approximately 13 DNA (total) adducts/10(8) nucleotides, or approximately 8 DNA (C-8) adducts/10(8) nucleotides. The presumed C-8 2-acetylaminofluorene/guanosine adduct, prepared by reaction of 2-acetoxy-2-acetylaminofluorene (2AAAF) with DNA, was a significant but unreliable marker of 2AAF/DNA adducts in the rat liver in vivo. DNA repair did not appear to remove DNA adducts selectively, and adducts remained in DNA when discernible DNA repair had ceased.

Structure-activity relationships for inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone lung tumorigenesis by arylalkyl isothiocyanates in A/J mice

Phenethyl isothiocyanate (PEITC), 3-phenylpropyl isothiocyanate (PPITC), 4-phenylbutyl isothiocyanate (PBITC), and the newly synthesized 5-phenylpentyl isothiocyanate (PPeITC), 6-phenylhexyl isothiocyanate (PHITC), and 4-(3-pyridyl)butyl isothiocyanate (PyBITC) were tested for their abilities to inhibit tumorigenicity and DNA methylation induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the lungs of A/J mice. Mice were administered isothiocyanates by gavage for 4 consecutive days at doses of 5, 1, or 0.2 mumol/day prior to administration of 10 mumol of NNK by i.p. injection. Mice were sacrificed 16 weeks after NNK administration and pulmonary adenomas were quantitated, PEITC effectively inhibited NNK-induced lung tumors at a dose of 5 mumol/day but was not inhibitory at doses of 1 or 0.2 mumol/day. PPITC, PBITC, PPeITC, and PHITC were all considerably more potent inhibitors of NNK lung tumorigenesis than PEITC. While virtually no differences in inhibitory activity could be ascertained for PPITC, PBITC, and PPeITC, PHITC appeared to be the most potent tumor inhibitor of all of the compounds. At a dose of 0.2 mumol/day, PHITC pretreatment reduced tumor multiplicity by 85%. PyBITC, an analogue of both NNK and PBITC, was ineffective as an inhibitor. Using the same protocol, the compounds were found to have qualitatively similar inhibitory effects on NNK-induced DNA methylation when administered at 1 mumol/day. These results extend our previous findings that increased alkyl chain length enhances the inhibitory activity of an arylalkyl isothiocyanate toward NNK lung tumorigenesis and demonstrate the exceptional chemopreventive potentials of two new isothiocyanates, PPeITC and PHITC.

Effects of type of dietary fat on phorbol ester-elicited tumor promotion and other events in mouse skin

Based on the biological activity of arachidonic acid metabolites, we hypothesized that alterations in the consumption of linoleic acid, the precursor to arachidonic acid, would result in a modification in tumor development when fed during the tumor promotion stage of the mouse skin initiation-promotion model. The effects of seven different levels of dietary linoleic acid (LA), supplied as corn oil in a 15% fat diet, on the incidence and rate of papilloma and carcinoma development were determined. SENCAR mice were placed on one of the experimental diets, containing 1.0, 3.6, 6.0, 7.9, 9.9, 12.5, or 15.0% corn oil, 1 week after initiation with 10 nmol of 7,12-dimethylbenz(a)anthracene and 3 weeks prior to the start of twice weekly promotion with 1 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA). At 15 weeks of TPA treatment there were significant differences in papilloma number among diet groups, such that an inverse correlation (r = 0.92) was observed between tumor number and level of corn oil; the lowest corn oil diet group had an average of 11.7 tumors/mouse, while the highest corn oil group had 5.4 tumors/mouse. However, there was little difference in tumor incidence among diet groups. A general relationship between diet and carcinoma incidence was also found, such that the highest corn oil diet group had the lowest carcinoma incidence. In an experiment performed with DBA/2 mice, the average number of papillomas/mouse at 17 weeks was 4.5 (1.0% corn oil), 5.6 (7.9%) corn oil), and 2.3 (15.0% corn oil). Papilloma incidence was also affected by diet, with a 79% incidence for the 15.0% corn oil and an incidence of 93% for the 1.0% corn oil group. analyses of the fatty acid composition of epidermal phospholipids in mice fed the experimental diets reflected the dietary LA levels, in that an accumulation of phospholipid LA, accompanied by an overall decrease in arachidonic acid, occurred with increasing dietary corn oil. In spite of the high membrane levels of LA, no measurable amount of epidermal conjugated dienes of LA could be detected. Epidermal prostaglandin E2 levels in acetone-treated mice were similar for all diet groups (approximately 3 pg/micrograms DNA). However, 6 h after topical application with 4 micrograms of TPA, prostaglandin E2 levels were elevated 5- to 10-fold; an inverse correlation (P less than 0.05) was seen with increasing dietary LA, although the concordance with decreased phospholipid arachidonic acid was not strong.(ABSTRACT TRUNCATED AT 400 WORDS)

Liver tumor promoting ability of corn oil gavage in B6C3F1 male mice

In chronic carcinogenic bioassays, chemicals being tested with low water solubility have been administered via corn oil gavage. The present study examined the effect of chronic corn oil gavage on hepatic tumor formation in the B6C3F1 male mouse. Mice were initiated with diethylnitrosamine (DENA) either at 15 days of age with a single i.p. injection (5 micrograms/gbw) (protocol 1) or at 4 weeks of age via the drinking water (15 mg/l) for a duration of 3 weeks (protocol 2). At weaning (protocol 1) or 8 weeks of age (protocol 2) initiated and untreated mice were administered either corn oil at a dose of 0.15 ml via gavage (once a day, 5 days/wk) or saline (0.15 ml via gavage, once a day 5 days/wk). All mice were killed at 28 weeks of age and hepatic lesions were quantitated. Only mice exposed to DENA demonstrated hepatic tumors. Mice treated with DENA (at 15 days of age) and corn oil gavage exhibited a significant decrease in the number of hepatic adenomas compared with DENA (at 15 days of age) only treated mice. No difference was noted in the number of hepatic adenomas between mice treated with DENA (at 4 wks of age) and corn oil gavage and mice exposed to DENA (at 4 wks of age) only.

Mutagenic lipid peroxides from edible oils

Weak mutagenic activity was detected in several commercially available edible palm and corn oils using liquid incubation bioassays with Salmonella typhimurium TA1537. Chromatographic fractionation of unrefined palm oil established that mutagenic activity was present in three fractions that also contained fatty acyl hydroperoxides. Similar weak mutagenic activity was also demonstrated for linoleic and linolenic acid hydroperoxides. In all cases, the mutagenicity was abolished by exogenous catalase, implying that the observed activity was moderated by hydrogen peroxide.

Neurotoxic effects of methylcyclopentadienyl manganese tricarbonyl (MMT) in the mouse: basis of MMT-induced seizure activity

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic manganese-containing compound which is used as an additive in unleaded gasoline. One neurotoxic effect of MMT in mice is seizure activity. In this study, seizures were observed in mice treated with MMT in propylene glycol or corn oil. The LD50 associated with seizure activity was lower in mice receiving MMT in propylene glycol (152 mg/kg) than in those receiving MMT in corn oil (999 mg/kg). Manganese concentrations in the brains of mice which showed seizure activity due to MMT were higher than in those that did not (2.45 micrograms/g vs. 1.14 micrograms/g for MMT treated in propylene glycol and 3.25 micrograms/g vs. 1.63 micrograms/g for MMT in corn oil). Mice treated with manganese chloride (MnCl2) showed increases in brain manganese comparable to those of the mice showing seizure activity due to MMT, but exhibited no sign of seizure activity. MMT in non-lethal seizure-inducing doses had no effect on the accumulation of 4-aminobutyric acid (GABA) in mouse brain. However, MMT inhibited the binding of t-[3H]t-butylbicycloorthobenzoate [3H]-TBOB (a ligand for the GABA-A-receptor linked chloride channel) in mouse brain membranes with an IC50 value of 22.8 microM. The data suggest that MMT (organic manganese) or a closely related metabolite and not elemental manganese itself is responsible for the seizure activity observed. The seizure activity may be the result of an inhibitory effect of MMT at the GABA-A receptor linked chloride channel.

Biological observations from feeding heated corn oil and heated peanut oil to rats

Five groups of male weanling rats were provided purified diets containing 15% by weight of either fresh or laboratory-heated corn oil (FCO, HCO) or fresh, laboratory-heated, or commercial pressure deep-fry peanut oil (FPO, HPO, PPO). Total weight gain, feed consumption, and feed efficiency were consistently greater for the FCO, FPO, and PPO groups. Although relative heart weights were unaffected, the HCO and HPO produced elevated liver and kidney weights. The dietary fats had no effect on the hematological status of the animals or the proportions of cells comprising the total leukocytes of the blood. Physical, chemical, and microscopic evaluation of the urine detected no pathologic conditions. Rats fed diets containing HCO or HPO demonstrated toxicity of thermally oxidized fats by the appearance of diarrhea, dermatitis, seborrhea, and hair loss. Histological examinations revealed injury of the thymus by all fat samples except the FCO; the liver was damaged by the HCO, HPO, and PPO, and the testes and epididymides by HPO and PPO. In the latter case there was complete cessation of spermatogenesis.

Proliferative exocrine pancreatic lesions in rats. The effect of sample size on the incidence of lesions

Pancreatic tissue from untreated and corn oil gavage control rats in four chronic (2-year) toxicity and carcinogenicity studies was examined microscopically for the presence of acinar hyperplasia, acinar adenoma, and acinar carcinoma. Formalin-fixed pancreatic tissue that had been saved from these rats was then examined for grossly visible lesions; and all additional available pancreatic tissue was embedded, routinely processed, and sectioned at 5-7 microns for histopathological examination. There were no additional gross lesions identified in the review of the residual tissues. However, microscopic examination of this additional tissue resulted in a marked increase in the number of proliferative lesions diagnosed. The incidence of acinar cell adenomas increased from 1/188 (0.5%) to 28/193 (15%) in untreated control male rats and from 8/194 (4%) to 73/195 (37%) in corn oil gavage vehicle control male rats. There were similar increases in hyperplasia in vehicle and untreated male rats, and similar but much less dramatic increases in hyperplasia and adenoma in vehicle and untreated control female rats. The previously reported effect of increased proliferative lesions of the exocrine pancreas of male rats given corn oil vehicle was confirmed. In addition, examination of a larger tissue sample identified a similar but smaller effect of the corn oil vehicle in female F344 rats that had not been detected by routine sampling of the pancreas.

Enhancement of the hepatotoxicity of chloroform in B6C3F1 mice by corn oil: implications for chloroform carcinogenesis

A recent study of the ability of chloroform in drinking water to produce cancer reported that male Osborne-Mendel rats developed renal tumors, but that female B6C3F1 mice failed to develop hepatocellular carcinomas. The results obtained in the male Osborne-Mendel rats were comparable to those observed in an earlier study sponsored by the National Cancer Institute (NCI). On the other hand, the lack of an increased incidence of hepatocellular carcinomas in female B6C3F1 mice was in sharp contrast to previously reported results. The doses of chloroform used were comparable to that which produced an 85% incidence in the NCI study. We have investigated the extent to which the vehicle might be responsible for the different results in these two studies by examining the differential effects of chloroform when it was administered by gavage using corn oil versus a 2% Emulphor suspension as the vehicle. Male and female B6C3F1 mice were administered chloroform at 60, 130, and 270 mg/kg per day for 90 days. At sacrifice, body and organ weights were measured, and blood was recovered to perform the following serum chemistry measurements (in order of priority): glutamate oxalacetate transaminase (SGOT), lactate dehydrogenase (LDH), blood urea nitrogen (BUN), and triglyceride (TG) levels. The liver was sectioned for histopathological examination. Chloroform increased SGOT levels significantly only when administered in corn oil at a dose of 270 mg/kg in both male and female mice. It had no effect on LDH activity. There was a small increase in BUN when chloroform was administered in corn oil, but not when administered in 2% Emulphor. When administered in corn oil, chloroform significantly decreased serum TG levels but was without effect on this parameter when administered in 2% Emulphor. Chloroform decreased body weight and increased liver weight with both vehicles, but the effects were significantly greater when it was administered in corn oil. Mice administered chloroform in corn oil displayed a significant degree of diffuse parenchymal degeneration (5 of 10 males and 1 of 10 females) and mild to moderate early cirrhosis (5 of 10 males and 9 of 10 females); significant pathological lesions were not observed in the animals administered corn oil without chloroform nor in mice receiving chloroform in 2% Emulphor. These data indicate that administration of chloroform by corn oil gavage results in more marked hepatotoxic effects than observed when it is provided in an aqueous suspension.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of gavage vehicle on hepatotoxicity of carbon tetrachloride in CD-1 mice: corn oil versus Tween-60 aqueous emulsion

This investigation was conducted to evaluate the effect of gavage vehicles on altering the severity of the subchronic hepatotoxicity of carbon tetrachloride (CCl4). Male and female CD-1 mice were gavaged with 0, 1.2, 12, and 120 mg/kg CCl4 in either a corn oil or 1% Tween-60 vehicle once daily for 5 consecutive days per week for 90 days. The study revealed that the hepatotoxicity was greater in the mid- and high-dose groups of mice that had received CCl4 administered in corn oil. Increases in serum enzyme activities were detected in the mid-dose groups of mice that were gavaged with CCl4 in corn oil. The serum enzyme activities were significantly higher in the high-dose groups of animals in which CCl4 was administered in corn oil. Histopathological findings indicated that hepatocellular changes following the administration of CCl4 at the mid- and high-dose levels were more frequent and more severe when CCl4 was given in corn oil than when it was administered in Tween-60. The experimental findings indicate that the no-observed-adverse-effect level from CCl4 exposure was lowered by an order of magnitude (from 12 to 1.2 mg/kg) and that the hepatotoxicity of CCl4 was enhanced in the high-dose treatment groups when corn oil was employed as the gavage vehicle.