Around the fresh 1900s, boffins examined to own lipophilicity by the taking a look at the consumption of nonpolar ingredients playing with all-natural solvents, such as for instance octanol, since a great surrogate towards the organic number present in bacteria (345)
The new dynamics regarding killer accumulation during the and you may release out of At is based on the physic-toxins characteristics. This new partition coefficient seems getting a major parameter governing the brand new consumption off lipophilic toxicants for the adipocytes. However, even within a good toxicant classification, architectural determinants dictate physico-chemicals qualities that dictate At the accumulation. Eg, more PCB congeners can show distinct uptake and you will sites character into adipocytes (54) (250) (249). You to definitely investigation compared the fresh accumulation prospective from inside the From the off around three PCB congeners: PCB ?twenty eight, ?153, and you may ?118 based on each of the congeners physico-chemical have. Results indicated that the fresh new figure regarding accumulation ranged amongst the congeners due to molecular proportions, molecular frequency, and lipophilicity (54). Specifically, the degree of halogenation, or count and you can position from chlorine substituents into the PCBs, influenced their uptake and you will buildup during the adipocytes. PCB-twenty-eight registered adipocytes faster versus most other a couple congeners almost certainly simply because of its reduced molecular lbs, dimensions, and lipophilicity, if you are PCBs ?153 and ?118 remained swept up regarding the lipophilic phone membrane layer and you may diffused even more slowly to the intracellular, hydrophobic cytoplasm of one’s adipocyte (54).
The product quality approach takes on that structure try “move restricted,” for example the venous blood making the newest organ was at harmony on the “well-stirred” muscle storage space (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 Yazar hakkÄ±nda daha fazla 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.