Division of mitochondria in cultured human fibroblasts

Ovate mitochondria in cultured human fibroblasts divide by pinching. In the process, as observed by transmission electron microscopy, a deep incisure of the surface membranes separates the organelle into two lobes connected by a slender isthmus. A single element of smooth endoplasmic reticulum (SER) invariably accompanies each incisure, extending deep into the cleft. When the ingrowing membranes meet and fuse with the antipodal membranes, fission occurs. Elongated mitochondria that give no indication of division often are cloaked by a single, continuous cistern of SER.

Metabolism of 1-nitropyrene in mice: transport across the placenta and mammary tissues

The distribution and metabolism of the environmental pollutant 1-nitropyrene was studied in C57B1/6N mice following oral or intraperitoneal dosing. When administered by gavage, 1-nitropyrene and its metabolites demonstrated biphasic elimination kinetics from the blood, with half-lives of 0.3 and 1.8 days and a distribution volume of 74 ml. Intraperitoneal administration resulted in similar biphasic elimination, with half-lives of 0.5 and 3 days and a distribution volume of 98 ml. Treating pregnant C57B1/6N (C3H sire) mice by gavage resulted in similar absorption and elimination kinetics of 1-nitropyrene and metabolites, except that the distribution volume increased to 123 ml. 1-Nitropyrene and/or its metabolites (0.7% of the administered dose) crossed the placenta and accumulated in the fetuses and amniotic fluid, with both C-oxidized and nitroreduced metabolites being detected. Suckling neonates accumulated 1-nitropyrene and its metabolites when their dams were administered 1-nitropyrene by gavage. Each neonate received approximately 0.1% of the administered dose and demonstrated the presence of both C-oxidized and nitroreduced metabolites. These results demonstrate that this environmental pollutant is capable of crossing the placenta or mammary tissues to expose the offspring to a potentially genotoxic compound.

Mutagenicity of the phenolic microsomal metabolites of 3-nitrofluoranthene and 1-nitropyrene in strains of Salmonella typhimurium

The environmental pollutant 3-nitrofluoranthene is metabolized in vitro and in vivo to several products including the phenolic metabolites 3-nitrofluoranthen-6-ol (3NF-6-ol), 3-nitrofluoranthen-8-ol (3NF-8-ol), and 3-nitrofluoranthen-9-ol (3NF-9-ol). Similarly, 1-nitropyrene is metabolized to the phenolic metabolites 1-nitropyren-3-ol (1NP-3-ol), 1-nitropyren-6-ol (1NP-6-ol), and 1-nitropyren-8-ol (1NP-8-ol). The mutagenicity of these compounds was investigated using strains of Salmonella typhimurium deficient in either certain nitroreductases or the aryl hydroxylamine O-esterificase. In TA98, 3-nitrofluoranthene and 3NF-8-ol were equally mutagenic at approximately 10(3) revertants/nmole while 3NF-6-ol and 3NF-9-ol were 10-fold less mutagenic. 1-Nitropyrene and 1NP-3-ol likewise were equally mutagenic at approximately 700 revertants/nmole and 1NP-6-ol and 1NP-8-ol were 100-fold less mutagenic. The mutagenicity of 1-nitropyrene was dependent on the 'classical nitroreductase' which is absent in TA98NR, and that of 3-nitrofluoranthene, 3NF-8-ol, and 1NP-3-ol was less dependent on this nitroreductase. Using TA98/1,8DNP6, it was determined that the mutagenicity of 3-nitrofluoranthene, 3NF-8-ol, and 1NP-3-ol but not 1-nitropyrene was dependent on the presence of the O-esterificase. 3-Nitrofluoranthene and 3NF-8-ol were mutagenic in TA100, while 3NF-6-ol and 3NF-9-ol were considerably less mutagenic. 3-Nitrofluoranthene was not mutagenic in TA100NR nor in TA100-Tn5-1,8DNP1012. None of the phenolic metabolites of 3-nitrofluoranthene were mutagenic in TA100-TN5-1,8DNP1012 indicating a strong dependence for mutagenicity on the O-esterificase or the 1,8-dinitropyrene nitroreductase which is absent in this strain. These results are discussed in view of possible mechanisms for the differences in the mutagenicity of the phenolic metabolites of these two nitrated arenes.

Liver microsomal metabolism of the environmental carcinogen 3-nitrofluoranthene. I. Phenolic metabolites

The liver microsomal metabolism of the environmental carcinogen 3-nitrofluoranthene has been investigated. Five phenolic metabolites were isolated and characterized by their mass and NMR spectra as: 3-nitrofluoranthen-1-ol, 3-nitrofluoranthen-6-ol, 3-nitrofluoranthen-(7 or 10)-ol, 3-nitrofluoranthen-8-ol and 3-nitrofluoranthen-9-ol. While the microsomes isolated from Sprague-Dawley rat liver and C57B16 mouse liver preferentially metabolized the 3-nitrofluoranthene to 3-nitrofluoranthen-8-ol and 3-nitrofluoranthen-9-ol, the microsomes from Hartley guinea-pig liver preferentially metabolized 3-nitrofluoranthene to 3-nitrofluoranthen-6-ol. 3-Nitrofluoranthen-1-ol was a minor metabolite in each of the incubations. The results indicate the presence of the nitro group on fluoranthene directs the metabolism away from the C1-C5 positions, and more towards the C6-C10 positions.

Differing effects of chronic ethanol consumption by mice on liver microsomal metabolism of xenobiotics: 1-nitropyrene, nicotine, aniline, and N-nitrosopyrrolidine

The effect of ethanol consumption by male CF-1 mice on liver microsomal enzyme activities has been investigated. The total microsomal cytochrome P-450 content was increased by 38%, while cytochrome b5 was decreased by 31%, which are characteristic alterations in liver microsomes following ethanol consumption. Other alterations included a decreased NADPH cytochrome c reductase activity and increased NADPH-supported rates of N-nitrosopyrrolidine and aniline hydroxylation. While ethanol consumption did not alter the total metabolism of nicotine, the rates of N- and C-hydroxylation were differently affected. The 5'-hydroxylation of nicotine was increased by 83%, while the N'-oxidation was decreased by 31%. Changes in the microsomal metabolism of the environmental carcinogen 1-nitropyrene included a slight reduction in the overall metabolism, which can be accounted for by a reduction in the formation of one phenolic metabolite, 1-nitropyren-3-ol.