Microsomes composition

Poulin P, Haddad S. 2011. Microsome composition-based model as a mechanistic tool to predict non-specific binding in liver micro-somes. J Pharm Sci 100 4501-4517. 

Fig. 1. Relative composition of root microsomal membranes from 24 land races, varieties and breeding lines of rice which differ in their salt resistance. Campesterol, Stigmasterol and Sitosterol as % of total sterols 16 0, 18 1, 18 2 and 18 3 fatty acids as % of total fatty acids Na transport on a relative scale from (1) lowest to (9) highest. Data of D.R. Lachno, T.J. Flowers A.R. Yeo (unpublished).

Analysis of reaction mixtures for 1-propanol and 2-propanol following incubation of NDPA with various rat liver fractions in the presence of an NADPH-generating system is shown in Table I ( ). Presence of microsomes leads to production of both alcohols, but there was no propanol formed with either the soluble enzyme fraction or with microsomes incubated with SKF-525A (an inhibitor of cytochrome P450-dependent oxidations). The combined yield of propanols from 280 ymoles of NDPA was 6.1 ymoles and 28.5 ymoles for the microsomal pellet and the 9000 g supernatant respectively. The difference in the ratio of 1- to 2-propanol in the two rat liver fractions may be due to differences in the chemical composition of the reaction mixtures (2) Subsequent experiments have shown that these ratios are quite reproducible. For comparison, Table I also shows formation of propanols following base catalyzed decomposition of N-propyl-N-nitrosourea. As expected (10,11), both propanol isomers were formed, the total yield in this case being almost quantitative. 

Each entry is an average of data obtained from two separate experiments using different microsomal preparations. Enantiomeric composition was determined by CD spectral data (18) and by CSP- HPLC (19,20). 

Figure 3. Mechanism of microsomal EH-catalyzed hydration of the K-region epoxide enantiomers of BA, BaP, and DMBA. The percentages of the trans-addition product by water for each enantiomeric epoxide are indicated. The enantiomeric composition of the dihydrodiol enantiomers formed from the hydration of DMBA 5S,6R-epoxide was determined using 1 mg protein equivalent of liver microsomes from pheno-barbital-treated rats per ml of incubation mixture and this hydration reaction is highly dependent on the concentration of the microsomal EH (49). The epoxide enantiomer formed predominantly from the respective parent hydrocarbon by liver microsomes from 3-methylcho-lanthrene-treated rats is shown in the box.

Table II. Enantiomeric Composition of the 3,4- and 5,6-Dihydrodiols Formed in the Metabolism of BA and DMBA by Liver Microsomes from Rats of the Sprague-Dawley Strain...

Devineau, J. and C. Amiard Triquet 1985. Patterns of bioaccumulation of an essential trace element (zinc) and a pollutant metal (cadmium) in larvae of the prawn Palaemon serratus. Mar. Biol. 86 139-143. Dib, A., J.P Clavel, and J.P. Carreau. 1989. Effects of gamma-linolenic acid supplementation on lipid composition of liver microsomal membranes. I. Pregnant rats fed a zinc-deficient diet and those fed a balanced one. Jour. Clin. Biochem. Nutr. 6 95-102. 

Electron microscopic examination of midge microsomes prepared by a slightly different procedure than Table VIII revealed a homogeneous mixture of vesicles derived from rough and smooth endoplasmic reticulum, ribosomes and a few mitochondria. Midge preparations are similar in composition to microsomal fractions of southern armyworm fat body and gut (44). 

Reductive dechlorination of penclomedine was, indeed, observed with liver microsomes under anaerobic conditions, indicating that a composite sequence such as this should not be dismissed without the benefit of further investigations. Given that the dehalogenation reactions exemplified by tri-fluridine and penclomedine may be less uncommon than implied here, mechanistic studies designed to clarify these processes would be most welcome. 

Garfinkel, D. (1958) Studies on pig liver microsomes. I. enzymic and pigment composition of different microsomal fractions. Arch. Biochem. Biophys. 77, 493-509. 

Adversely affects phospholipid composition and synthesis in roots and microsomes from seedlings by inhibition of choline phosphotransferase (6)... 

Composition of human liver microsomes as reported by Shimada et al. (1994)... 

Bailie, M. J. and Morton, R. K. 1958. Comparative properties of microsomes from cow s milk and from mammary gland. 2. Chemical composition. Biochem. J. 69, 44-53. 

Hagar, A.F. and Hazel, J.R. (1985). Changes in desaturase activity and the fatty acid composition of microsomal membranes from liver tissue of thermally-acclimating rainbow trout. Journal of Comparative Physiology 156B, 35-42. 

The composition of the metabolite mixtures shows a quantitative dependence on species. Table 2 compares the transformation of A 1-THC by rat and mouse liver microsomes under similar conditions. While the principal products were the same in both species, there... 

When guinea pigs were fed diets supplemented with oil related to TOS, the TOS-related oil produced a decrease in lipid peroxidation products with minimal alterations in phospholipids fatty acid composition of liver microsomes (358). TOS is an exogenously induced autoimmune disease in humans, believed to be a... 

Kaminsky, L. S., Dunbar, D. A. Wang, E E, Beaune, E, Larrey, D., Guengerick, E E, Schnellmann, R. G., and Sipes, 1. G. (1984). Human Hepatic Cytochrome P450 Composition as Probed by in vitro Microsomal Metabolism of War-farine, Drug Metab. Disposition, 12 470-476. 

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