In vitro formation of organ specific proximate carcinogen of benzo(a)pyrene by rat homogenates.

In order to determine the organ specific carcinogenicity of benzo(a)pyrene (B(a)P), its metabolites, formed in vitro by incubation with the homogenates from liver, lungs, kidneys, intestine and brain of rats, were isolated by TLC and spectroscopy. B(a)P was found to be converted into a number of metabolites by different tissue homogenates. The results showed that the proximate carcinogenic metabolite, 7,8-dihydro-7,8-dihydroxy B(a)P was formed only when rat lung and kidney homogenates were incubated with B(a)P in vitro. The UV spectral analysis also confirmed the formation of this metabolite only on incubation of B(a)P with rat lung and kidney homogenates. As the proximate carcinogenic metabolite was only formed by incubating B(a)P with the homogenates from target organs, its organ specific carcinogenicity may be explained.

Assay of carcinogenicity of tobacco metabolites employing microsomal degranulation technique.

Carcinogenicity of salivarty extracts of different types of tobaccos smoked and chewed in India and Pan Parag were tested using microsomal degranulation technique. Results obtained on the basis of RNA/protein ratios (Indices to confirm the detachment of ribosomes from microsomes) showed that tobaccos used for cigarette, bidi, hukah and chewing tobacco with lime as well as Pan Parag were positively carcinogenic. Two fractions out of 7 isolated chromatographically from salivary extract of chewing tobacco plus lime were found to be carcinogenic. Elemental and spectral analyses indicated that the fractions are possibly an aromatic compound with an aliphatic side chain and N-(buty1 nitrosamine)-1-(3-pyridyl)-4-hydroxy-1-butanone.

Rapid detection of chemical carcinogens by measuring RNA released from microsomes in post-mitochondrial supernatant.

Incubation of carcinogens with post-mitochondrial supernatant (PMS) and NADPH releases ribosomes from microsomes resulting in increased RNA concentration in post-microsomal supernatant. However, non-carcinogens fail to do so. Enhanced concentration of RNA in test over control samples can provide a useful index for the carcinogenicity of environmental pollutants.

Elevation in diacylglycerol level and activation of protein kinase C in liver of mice administered with carcinogenic dose of 1,2-dimethylhydrazine.

Five weeks treatment of male mice with 1,2-dimethylhydrazine leads to elevation in the level of diacylglycerol in liver. Increase in diacylglycerol content is accompanied by an increase in particulate activity of protein kinase C with a fall in its activity in cytosolic fraction. Quantitative analysis of neutral lipids of different subcellular fractions from liver reveals that diacylglycerol levels increases highly significantly in liver microsomal membranes of carcinogen treated mice. Separation of neutral lipids by thin layer chromatography indicates that also there is an increase in cholesterol esters in nuclei, mitochondria and microsomes of mice liver whereas monoacylglycerol almost disappeared in mitochondria and microsomes after DMH administration in comparison to their respective controls.