As soon as this new 1900s, scientists checked out to possess lipophilicity because of the taking a look at the consumption of nonpolar compounds having fun with normal solvents, like octanol, because the a great surrogate on organic count contained in bacteria (345)
This new fictional character regarding toxin buildup for the and you may release away from In the would depend to their physic-toxins qualities. The fresh new partition coefficient has proven become a primary parameter governing the new use away from lipophilic toxicants to your adipocytes. Although not, also in this an effective toxicant class, structural determinants dictate physico-chemicals qualities you to definitely influence On accumulation. Such, more PCB congeners can display collection of consumption and you can shops fictional character towards adipocytes (54) (250) (249). That analysis compared brand new buildup potential when you look at the At off three PCB congeners: PCB ?twenty-eight, ?153, and you may ?118 centered on each of the congeners physico-toxins keeps. Abilities revealed that brand new character out of buildup varied involving the congeners due to molecular dimensions, molecular volume, and you may lipophilicity (54). Especially, the level of halogenation, or amount and condition out-of chlorine substituents with the PCBs, swayed the uptake and you can accumulation when you look at the adipocytes. PCB-twenty-eight joined adipocytes more rapidly versus other a couple congeners almost certainly because of its reduced molecular weight, proportions, and you may lipophilicity, when you’re PCBs ?153 and you will ?118 stayed trapped regarding lipophilic mobile membrane layer and https://datingranking.net/tr/dating4disabled-inceleme/ you will diffused so much more slowly towards the intracellular, hydrophobic cytoplasm of one’s adipocyte (54).
The quality means takes on your structure was “circulate minimal,” meaning that the latest venous blood leaving the body organ is at harmony towards “well-stirred” tissues area (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.