As soon as the latest 1900s, experts checked out getting lipophilicity because of the looking at the consumption off nonpolar compounds having fun with all-natural solvents, for example octanol, just like the a surrogate for the all-natural amount contained in organisms (345)
This new personality off killer buildup into the and you can discharge of Within would depend on their physic-toxins characteristics. New partition coefficient has proven as a major factor ruling new use out of lipophilic toxicants with the adipocytes. not, even inside an effective toxicant class, structural determinants dictate physico-chemical substances functions one to dictate On accumulation. Including, various other PCB congeners can show line of consumption and sites character with the adipocytes (54) (250) (249). You to studies opposed brand new accumulation potential when you look at the At the away from three PCB congeners: PCB ?28, ?153, and you can ?118 predicated on each one of the congeners physico-chemicals have. Show showed that new dynamics regarding buildup ranged within congeners due to unit proportions, unit frequency, and you can lipophilicity (54). Especially, the level of halogenation, or number and updates off chlorine substituents towards PCBs, swayed the uptake and you can buildup inside the adipocytes. PCB-28 inserted adipocytes more rapidly compared to most other a couple of congeners almost certainly due to its shorter molecular lbs, size, and you will lipophilicity, when you’re PCBs ?153 and you will ?118 remained involved in the lipophilic cell membrane and you can diffused far more more sluggish with the intracellular, hydrophobic cytoplasm of the adipocyte (54).
The quality means assumes that the structure try “disperse minimal,” meaning that the newest venous bloodstream making Burada daha fazla keÅŸfet this new body organ is at equilibrium to the “well-stirred” cells compartment (232)
The lipophilicity of a compound depends on its chemical structure, where bigger, more complex and halogenated compounds are typically more lipophilic and resistant to biodegradation (206). Although not identical, the extent of chemical uptake from the water into the organic phase is proportional to what is expected and observed in organisms (345). The octanol-water partition coefficient (Kow) is defined by the following equation: Kow = Coctanol/Cwater, where Coctanol is the molar concentration of the compound in the octanol phase, and Cwater is the molar concentration of the compound in the aqueous phase when the system is at equilibrium (345). The adipose-serum partition coefficient determines the extent to which a chemical may accumulate in adipose (319); it is a ratio of the concentration of a chemical in adipose to serum at equilibrium. Typically, the distribution of xenobiotics into AT is dependent on a number of pharmacokinetic factors including tissue volume and blood flow (232). While this approach has proven valid for the distribution of various xenobiotics into tissues and organs, there are a number of chemicals for which this flow limited model has proven invalid, including highly lipophilic POPs (421) (190) (208) (232). These chemicals, along with other organic compounds, act according to a “diffusion-limited” model, which states that diffusion limitation is proportional to the octanol-water partition coefficient (Kow) of a chemical (232).
Ultimately, diffusion limitation increases as Kow increases. In support of the studies by Oberg et al. (294) who simultaneously measured PCB concentrations in rat plasma and adipose tissue, Levitt (232) found that hexachlorobenzene (HCB), hexabromobenzene, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and tetrabrominated dinenzo-p-dioxin (TBDD) have a “similar increase in diffusion limitation with increasing Kow.” Specifically, results of the study showed that the “apparent” rat adipose perfusion rate was smaller for a PCB (0.005kg/min/kg) with a log Kow greater than 7, while significantly larger (0.2 kg/min/kg) for chemicals with log Kow less than 5 (232). Collectively, these studies support the notion that at steady-state conditions, the log Kow, a measure of lipophilicity, can help predict the likelihood of a chemical to diffuse and accumulate into AT and contribute to steady-state body burdens. Table 3 provides an overview of the structures and partition coefficients of numerous POPs.
