Lipid content of tissue

Yuneva,. T.V., Shchepkina, A.M. and Shulman, G.E. (1994). The lipid content of tissues of squid from the tropical Adantic (In Russian). Gydrobiologicheskii Zhumal 30, 78-86. 

Mean lipid content of tissues were 62.0% in subcutaneous fat, 59.6% in omental fate, 8.3% in brain, and 4.5% in liver. 

No studies were located regarding distribution in humans following dermal exposure to PCBs. However, there is no evidence suggesting that distribution is route-dependent. Because of the lipophilic nature of these compounds, it would be reasonable to assume that once they are absorbed, PCBs will distribute to various tissues in proportion to their lipid contents. However, data from humans at autopsy suggest that the disposition of PCBs is congener and tissue specific and not based exclusively on the lipid content of tissues (Bachour et al. 1998 Dewailly et al. 1999 Schecter et al. 1994). Data regarding occupational exposure are discussed in Section 3.4.2. 

Distribution. Generally the highest concentration of PCB residues in fish are in tissues of high lipid content. In Table V juvenile coho salmon were fed equal amounts of three chlorobi-phenyls for 117 days. Fish were then killed and lipid content and PCB concentration of various tissues determined (33). Tissues are arranged from top to bottom in order of increasing PCB concentration. For most tissues, but not all, as lipid content increases so does PCB concentration. Lipid content and PCB concentration are low in liver and white muscle, intermediate in spinal column and lateral line muscle, and high in adipose tissue. Lipid content cannot be the sole determinant of PCB concentration in fish tissues because a discrepancy exists between lipid content of brain, heart and spleen and PCB concentration. 

Often we are interested in apolar or weakly monopolar pollutants (PCBs, chlorinated solvents, PAHs) and in organisms/tissues that contain significant lipid content (>5% on a dry weight basis). Also, investigators sometimes specially sample the fatty tissues (e.g., in some animals or humans). In such cases, the terms/iipC p or f ipKnipmei dominate in Eqs. 10-3 and 10-4 (see Illustrative Examples 10.1 to 10.3). Consequently it is reasonable to assume that the measured concentrations chiefly reflect the compounds present in the lipid phase and the concentrations can be normalized to the lipid content of the organism. Thus, the lipid normalized, K, bl0 hp, is simply given by ... 

Biomarker concentration Lipid content of body in adipose tissue (BL, grams)... 

Shchepkina, A.M. (1980b). The influence of helminths on the tissue lipid content of Black Sea anchovy and bullhead during the annual cycle. Technical Reports National Marine Fisheries Service, NOAA 25,49-51. 

Much higher levels of BHT were detected in mammary than in liver and serum. The difference appears to be due to the lipid content of the tissue which is ten times greater in mammary than in liver. BHT would be expected to be distributed equally in all lipid areas due to its lipophilic character. Its tissue concentration should then be dependent upon the level of lipids in any specific tissue. The lipid content could certainly account for the greater amounts of BHT found in mammary compared to liver tissues. 

Poulin and Krishnan (1995) developed a method to predict tissue blood PCs for incorporation into physiologically based pharmacokinetic (PBPK) models. Tissue blood partitioning was calculated as an additive function of partitioning into the water, neutral lipids and phospholipids constituent of individual tissues. These were calculated using published values for lipid and water content of tissues and the octanol-water PC of the compounds. Poulin and Krishnan (1998 1999) used this method to predict tissue blood PCs that were subsequently incorporated into a quantitative structure-toxicokinetic model. The prediction of tissue plasma PCs to describe distribution processes and as input parameters for PBPK models has been extensively researched by Poulin and coworkers a great deal of further information can be obtained from their references (Poulin and Theil, 2000 Poulin et al., 2001 Poulin and Theil, 2002a Poulin and Theil, 2002b). 

Forsythe, W.A., Miller, E.R., Hill, G.M., Romsos, D.R., and Simpson, R.C. 1980. Effects of dietary protein and fat sources on plasma cholesterol parameters, LCAT activity and amino acid levels and on tissue lipid content of growing pigs. J. Nutr. 110(12), 2467-2479. 

No studies were located in humans or animals regarding the distribution of 1,1-dichloroethane following inhalation exposure. However, since this chemical was once used as a gaseous anesthetic, it can be assumed that it is distributed to the central nervous system as well as to the other tissues of the body. Tissue uptake of halocarbons such as 1,1-dichloroethane is governed by the affinity of each tissue for the lipophilic chemical (i.e. the higher the lipid content of a tissue, the greater its uptake of 1,1-dichloroethane) (Sato and Nakajima 1987)... 

For mminant fat to become directly responsive to dietary unsaturated fats, it is necessary to protect the lipids against saturation by rumen microorganisms. The alteration of the lipid content of mutton by the feeding of such protected oil supplements has been described (14). Also, it has been shown that a diet of extruded soybeans increased the linoleic acid and linolenic acid contents of steer adipose tissue (15). 

General experience in increasing the n-3 lipids contents of eggs and poultry meat includes the following. The feeding of linseed oil, menhaden oil, and soybean oil to chickens has resulted in similar blood plasmas with VLDL and LDL lower than those fed chicken fat. The levels of C20 5n-3 in tissue lipids of chickens fed linseed oil approached those of chickens fed menhaden oil. Chickens fed linseed oil had the highest levels of polyunsaturates in tissues while those fed chicken fat had the lowest. Chickens fed soybean oil maintained the highest levels of linoleic (C18 2n-6) and arachidonic (C20 4n-6) acids in tissue lipids, but linseed oil and menhaden oil resulted in reduced C20 4n-6 content (112). Other researchers have also reported similar decreases in arachidonic acid, and increased levels of eicosapentaenoic (C20 5 -3) and docosahexaenoic (C22 6n-3) in the fatty acids of egg yolks from chickens fed menhaden oil (113-116). 

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