Isopentane is metabolized by hydroxylation to 2-methyl-2-butanol as the major metabolite, and 3-methyl-2-butanol, 2-methyl-1-butanol, and 3-methyl-1-butanol as minor metabolites in rat, mouse, rabbit, and guinea pig liver microsomes.
... Male mice of ICR strain were exposed to about 5% n-pentane for one hour while the oxygen in the environmental air was maintained at about 20%. Then their blood and liver tissue were collected and analyzed by means of GC and GC-MS. The metabolites thus obtained were 2-pentanol, 3-pentanol and 2-pentanone. The same procedure was repeated with isopentane; 3-methyl-2-butanol, 2-methyl-2-butanol and 3-methyl-2-butanone were detected as the resultant metabolites. In the presence of the NADPH-generating system liver microsomes were made to react to the substrate of saturated n-pentane or isopentane aqueous solution at 37 degrees C for one hour. As a result, the same metabolites were produced as obtained in the exposure experiment. It was therefore suggested that n-pentane and isopentane were metabolized chiefly by liver microsomes.
Pentane is absorbed following inhalation and ingestion, and to a small extent from dermal exposure. Once in the body it distributes to the tissues and blood, with the highest concentration in the adipose tissue. Pentane is metabolized by the cytochrome P-450 system. The main metabolite is 2-pentanol, followed by 3-pentanol, and 2-pentanone. These intermediates are further metabolized to glucuronic acid conjugates or oxidized to ketone products, which are excreted in the urine and expired air. (A600)
IDENTIFICATION AND USE: Isopentane is a volatile liquid or gas. It is used as a solvent, in the manufacture of chlorinated derivatives, and as a blowing agent for polystyrene. HUMAN STUDIES: Inhalation can cause dizziness, drowsiness, headache, and unconsciousness. Skin exposure leads to dry skin. Ingestion can cause nausea and vomiting. Isopentane is an aspiration hazard. If swallowed the substance easily enters the airways and could result in aspiration pneumonitis. Isopentane causes CNS depression between 270 and 400 mg/L, and is a weak cardiac sensitizer. High vapor concentrations are irritating to the skin and eyes. ANIMAL STUDIES: In dogs, 120,000 ppm isopentane was required to induce light anesthesia. Isopentane was lethal to dogs at levels of 150,000-170,000 ppm. Mice exposed to 90,000 ppm isopentane for 11 min showed light anesthesia. At higher concentrations (110,000 and 120,000 ppm), the CNS depression effect appeared within 4 and 2 min, respectively. In rats, no treatment-related effects of isopentane were found in relation to the reproductive capacity of parental animals or the pre- and post-natal development of the F1 generation. There were no treatment-related effects in either gender at </= 300 mg/kg/day. The mutagenic activity of isopentane has been assayed using the Ames test. At concentrations of 100,000 ppm, it was not mutagenic in the presence and absence of a metabolic activating system.
Pentane is a central nervous system depressant and can cause loss of consciousness and coma at high doses. Ingestion may cause pulmonary toxicity due to pentane aspiration, including chemical pneumonitis, acute lung injury, and hemorrhage. Cardiovascular effects may include ventricular dysrhythmias and sudden death. (T29, A600)
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