Oxidation of n-hexadecane by subcellular preparations of guinea pig small intestine

Mineral oil in food, cosmetic products, and in products regulated by other legislations

For a few years, mineral oils and their potential adverse health effects have been a constant issue of concern in many regulatory areas such as food, cosmetics, other consumer products, and industrial chemicals. Analytically, two fractions can be distinguished: mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). This paper aims at assessing the bioaccumulative potential and associated histopathological effects of MOSH as well as the carcinogenic potential of MOAH for consumer-relevant mineral oils. It also covers the absorption, distribution, metabolism, and excretion of MOSH and MOAH upon oral and dermal exposures. The use and occurrence of consumer-relevant, highly refined mineral oils in food, cosmetics and medicinal products are summarized, and estimates for the exposure of consumers are provided. Also addressed are the challenges in characterizing the substance identity of mineral oil products under REACH. Evidence from more recent autopsy and biopsy studies, along with information on decreasing food contamination levels, indicates a low risk for adverse hepatic lesions that may arise from the retention of MOSH in the liver. With respect to MOAH, at present there is no indication of any carcinogenic effects in animals dermally or orally exposed to highly refined mineral oils and waxes. Such products are used not only in cosmetics but also in medicinal products and as additives in food contact materials. The safety of these mineral oil-containing products is thus indirectly documented by their prevalent and long-term use, with a simultaneous lack of clinical and epidemiological evidence for adverse health effects.

Short-term oral toxicity of gasohol in female rats

The systemic toxicity of gasohol (10% ethanol in gasoline by volume) in female rats following 4-week oral administration was studied. Female Sprague-Dawley rats (198+/-14 g) were divided into four groups of ten animals each. The low- and medium-dose groups received by gavage corn oil containing gasoline/ethanol at 16/1.8 and 160/18 (mg kg(-1) body weight), respectively, for 28 consecutive days. The high-dose animals were administered gasoline/ethanol at 1600/180 mg kg(-1) on the first day and the dose was reduced to 800/90 mg kg(-1) for the rest of the study period. Control animals received corn oil only. Urine was obtained from all rats after weeks 1, 2 and 4 for biochemical analysis. At termination of the study, kidneys of four rats from each group were examined by electron microscopy. Body weight gains, organ weights, tissue and organ histopathology, serum biochemistry, hematology, liver enzymes and biochemistry were determined in the remaining six animals of each group. No treatment-related changes were observed in the following endpoints: body weight gain or relative weights of the brain, lungs, liver, kidneys, spleen and thymus. A significant increase in pentoxyresorufin O-deethylase (PROD) and benzoylresorufin O-dealkylase (BROD) activities was detected in the high-dose animals, whereas ethoxyresorufin O-deethylase (EROD) activity was unchanged. Treatment with gasohol did not produce any significant changes in hematology and serum clinical chemistry parameters. Biomarkers of oxidative stress such as serum and liver thiobarbituric acid reactive substances (TBARS) and liver glutathione also were unaffected by treatments. Urinary ascorbic acid was elevated markedly in the medium- and high-dose groups following the first, second and fourth weeks of treatment. Urine hippuric acid was increased significantly in the high-dose groups. A dose-related increase in urinary aldehydes also was observed in animals after the first, second and fourth week of treatment. Interestingly, a separate 1-week dosing study revealed that the increase in urinary aldehydes was associated with gasoline and not with ethanol treatment. In the high-dose animals slight increases in urinary protein and N-acetylglucosaminidase activity were observed after week 1 but not after week 2 or week 4. No histopathological changes were detected in the liver, kidneys, stomach, brain, lungs or other tissues examined. Electron microscopic examination of the kidneys also did not reveal any abnormalities. It was concluded that short-term oral administration of gasoline/ethanol at 800/90 mg kg(-1) produced a biochemical response in the liver but no adverse effects in the kidneys and lungs. The biological significance of elevated urinary aldehydes at gasoline/ethanol concentrations of 160/18 mg kg(-1) and higher remains to be studied.

Abnormal n-nonacosane storage in humans: detection by gas chromatography/mass spectrometry of tissue extracts

We report a case of n-nonacosane storage disease, which went undiagnosed until the death of a 55-year-old farmer. Clinical, histological, and biochemical features are discussed. n-Nonacosane storage was identified by gas chromatographic-mass spectrometric analysis of different tissue extracts, n-nonacosane concentration reaching 1.2 mg g-1 of lung tissue and 0.32 mg g-1 of liver tissue. It was possible to rule out a work-induced intoxication, and n-nonacosane storage appeared to be accounted for by a lifelong, heavy consumption of unpeeled apples and Brussels sprouts.

Hydrocarbon hydroxylation system in liver microsomes from four animal species

The in vitro metabolism of n-heptadecane was investigated using hepatic microsomes from Hubbard chickens, New Zealand rabbits, Wistar rats and rainbow trout. Incubations with the 14C-labelled alkane for 1 hr showed that the rate of oxidation varied between species; the rate (per mg protein) in chickens was roughly 20-fold greater than the rate in trout, and roughly 10-fold greater than the rates in rats and rabbits. On the basis of cytochrome P-450 content, the rate of heptadecane metabolism was roughly 20-fold greater in the chicken than in the other species. Moreover, the lambda max Soret band of the reduced cytochrome P-450 CO-complex was observed at 452 nm in the chicken. Correlation between the rate of heptadecane metabolism and in vivo storage levels is discussed.

Hydrocarbons in hens injected with inactivated oil adjuvant vaccine

The radioactivity of different organs and tissues of laying hens injected with inactivated oil adjuvant vaccine containing [n-1-14C] octadecane was measured. It was shown that the hydrocarbons injected with the vaccination diffuse in relatively short periods of time to all the tissues, especially to those of the organs with greater blood supply, and that the hydrocarbons are largely eliminated by means of the eggs.

Hydrocarbons disposition, lipid content, and fatty acid composition in trout after long-term dietary exposure to n-alkanes

Uptake, distribution, and storage of n-alkanes was studied in rainbow trout receiving a diet containing 1% normal paraffins in the C13-C22 range. After 3 months, the concentration of hydrocarbons deposited in the whole body reached a steady equilibrium value in the range 700-900 ppm. The most pronounced deposition occurred in the adipose tissue. The n-alkane pattern in the whole body exhibited a profile different from that of the alkane mixture ingested. The alkanes around C20 were not retained to any great extent, but as the chain length decreased, the relative amount stored increased. In the liver a marked predominance of even-carbon chain length was observed while in whole fish and in other organs such a phenomenon did not occur. After 5 months, total lipids in the carcass were significantly lower in the test group than in the control group. At the end of the accumulation period, a significant enhancement in the proportion of odd- and even-chain saturated fatty acids from C14:0 to C18:0 was noted in carcasses of hydrocarbon-fed fish. Myristic, pentadecanoic, and heptadecanoic acids were also significantly more abundant in the liver and adipose tissue of contaminated fish. This increase is attributed to the terminal oxidation of the predominant n-alkanes in the diet into the corresponding fatty acids. During the depuration period, one-half of the trout in each group were fed a hydrocarbon-free diet, while the others were starved. After 2 months, both starved and fed trout had lost approximately 50% of the amount of total n-alkanes stored. The n-alkanes longer than C16 were well retained, while short-chain alkane concentration decreased rapidly.

Metabolism of naphthenic hydrocarbons. Utilization of a monocyclic paraffin, dodecylcyclohexane, by rat

3H-Dodecylcyclohexane was incorporated in rat diet in order to study the metabolic utilization by mammals of a monocycloparaffin chosen as a typical naphthenic constituent of mineral oils. Dodecylcyclohexane was largely absorbed. No elimination of the hydrocarbon was observed in urine while an extended excretion of 3H occurred via this route. About 7% of absorbed dodecylcyclohexane was stored in the carcass, while the rest was omega-oxidized to cyclohexyldodecanoic acid, which incorporated into neutral lipids and phospholipids. The aliphatic chain of this unusual fatty acid underwent the normal fatty acid degradation pathways, leading to even fatty acids, squalene, cholesterol and nonlipid resynthesis, while the cyclohexyl ring was eliminated as urinary metabolites. Incorporation of omega-cyclohexyl fatty acids in phospholipids may raise a point of toxicological significance which is to be investigated.

Metabolism of a n-paraffin, heptadecane, in rats

14C-heptadecane incorporated in rat diet was largely absorbed, and a balance study showed extensive 14CO2 excretion (65%). There was no elimination of the hydrocarbon in the urine, and only minute quantities of labeled metabolites. Radioactivity in the feces was entirely in heptadecane. About 7% of the heptadecane absorbed was stored in the carcass, whereas the rest was omega-oxidized to heptadecanoic acid. This fatty acid was incorporated into neutral lipids and phospholipids, underwent the normal fatty acid degradation pathway, and contributed to the synthesis of lipids, including fatty acids, squalene and cholesterol, and nonlipids (7-10%). Heptadecanoic acid was desaturated to heptadecenoic acid. The even distribution of radioactivity in the fatty acids of the various phospholipid classes indicated that heptadecane did not interfere with the biochemical mechanisms of these functional lipids.