The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis an...

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Creatine and Creatinine Metabolism

Role of N-nitroso compounds (NOC) and N-nitrosation in etiology of gastric, esophageal, nasopharyngeal and bladder cancer and contribution to cancer of known exposures to NOC.

Biological activities of oxysterols

Cholesterol autoxidation 1981-1986.

Integrated Science Assessment for Oxides of Nitrogen — Health Criteria

N-nitrosoatrazine : synthesis, kinetics of formation, and nuclear magnetic resonance spectra and other properties

Identification of cholesterol as a mouse skin lipid that reacts with nitrogen dioxide to yield a nitrosating agent, and of cholesteryl nitrite as the nitrosating agent produced in a chemical system from cholesterol.

We examined the mutagenicity of iso-butyl nitrite (IBN) vapor and aqueous IBN solution in the Ames test to help evaluate the hazard of sniffing this vapor, a habit which might play a role in the induction of Kaposi's sarcoma associated with acquired immune deficiency syndrome. Chemical analysis showed that the saturated vapor contained 190 micrograms IBN/ml at 25 degrees C, and saturated aqueous solution, 2.6 mg IBN/ml at 21-23 degrees C. When agar plates containing Salmonella typhimurium TA-1535 and rat liver S-9 were exposed to IBN vapor, the number of mutants reached a maximum after 40 min. A mean of 307 mutants/plate (22 x background) was observed when the plates were exposed to IBN vapor for 30 min. Addition of 0.2 ml saturated IBN solution in water to similar plates gave a mean of 179 mutants/plate (7.9 x background) in the absence of S-9, confirming published results. The S-9 did not affect the results. Based on the IBN level in medium exposed to IBN vapor, the vapor was apparently 11 times more mutagenic than IBN solution. This was attributed to continuous replenishment of unstable IBN in the medium by the vapor. The half-life of IBN at 21-23 degrees C was > 1 hr for solutions in water and < 3 min for solutions in the assay medium. This instability was traced to a reaction with phosphate, presumably hydrolysis to nitrite and iso-butanol. IBN in solution was 2.8 times more mutagenic than sodium nitrite, suggesting that IBN was not mutagenic because of its conversion to nitrite. Iso-butanol was not mutagenic. The results demonstrate the potential hazard of sniffing IBN vapor.

Mutagenicity of iso-butyl nitrite vapor in the Ames test and some relevant chemical properties, including the reaction of iso-butyl nitrite with phosphate.

Hydroxylation and dealkylation of methyl-n-butylnitrosamine and role of certain cytochrome P-450 isozymes in these reactions.

Skin lipids of mice exposed to NO2 contain lipid-soluble nitrosating agent(s) (NSA) that react in vitro with amines to produce nitrosamines. To test whether this reaction occurs in skin, we exposed mice to 50 ppm NO2 for 4 h and, 20 h later, applied 25 mg morpholine or N -methylaniline to the skin, which was then analyzed for the corresponding nitrosamine. When morpholine was applied, mean N -nitrosomorpholine yield was only 0.3 nmol/mouse (not significant). When N -methylaniline was applied and mice were killed after 10–40 min, N -nitroso- N -methylaniline yield in the skin was 13–21 nmol/mouse of which 87% occurred in the hair. NSA formation when mice were exposed to 6.5 ppm NO2 was only 0.15% of that for exposure to 50 ppm NO2. NSA occurred mostly in surface lipids of the skin and its in vitro reaction to give nitrosamines was not inhibited by α-tocopherol. When morpholine was painted and mice were then exposed to 55 ppm NO2 for 30 min, the skins contained 19 nmol N -nitrosomorpholine/mouse, attributed to a direct reaction between NO2 and the amine. We concluded that nitrosamine formation in skin by this direct reaction may be more important than the reaction of amines with NO2-derived NSA.

David M. Babcook

Papers

N-nitrosoatrazine : synthesis, kinetics of formation, and nuclear magnetic resonance spectra and other properties

Identification of cholesterol as a mouse skin lipid that reacts with nitrogen dioxide to yield a nitrosating agent, and of cholesteryl nitrite as the nitrosating agent produced in a chemical system from cholesterol.

Mutagenicity of iso-butyl nitrite vapor in the Ames test and some relevant chemical properties, including the reaction of iso-butyl nitrite with phosphate.

Hydroxylation and dealkylation of methyl-n-butylnitrosamine and role of certain cytochrome P-450 isozymes in these reactions.

Nitrosamine formation from amines applied to the skin of mice after and before exposure to nitrogen dioxide.