Lipophilic substances accumulation

Diffusion (A). Lipophilic substances (red dots) may enter the membrane from the extracellular space (area shown in ochre), accumulate in the membrane, and exit into the cytosol (blue area). Direction and speed of permeation depend on the relative concentrations in the fluid phases and the membrane. The steeper the gradient (concentration difference), the more drug will be diffusing per unit of time (Pick s Law). The lipid membrane represents an almost insurmountable obstacle for hydrophilic substances (blue triangles). 

It is also important to consider the potential for a substance to accumulate or to be retained within the body. Lipophilic substances have the potential to accumulate within the body if the... 

A -THC is rapidly distributed to all tissues despite being tightly bound by plasma proteins. A -THC is a highly lipophilic substance and so accumulates in tissue high in lipid content. Traces of A -THC have been found in adipose tissue more than 30 days after the subject smoked a single joint. The terminal half-life of A -THC in plasma ranges from 18 hours to 4 days. 

Children are exposed to PBBs and PBDEs in the same manner as the general population, primarily via coiisiiinptioii of contaminated foods. Exposure also may occur by transfer of PBBs and PBDEs that have accumulated in women s bodies to the fetus across the placenta. Because PBBs and PBDEs are lipophilic substances, they can additionally accumulate in breast milk and be transferred to nursing infants. Placental transfer, although it may be limited in absolute amounts, is a concern because of possible effects of PBBs and PBDEs on sensitive immature tissues, organs, and systems, with potentially serious long-lasting consequences. Transfer of PBBs and PBDEs via breast milk could be relatively considerable and, like prenatal exposure, has the potential to contribute to altered development. 

Since DEHP is a lipophilic substance, it has the potential to accumulate in maternal milk and be transferred to suckling offspring. Both DEHP (216 pg/mL) and MEHP (25 pg/mL) were detected in the milk collected from lactating Sprague-Dawley rats 6 hours after the last of three daily gavage doses of 2,000 mg DEHP/kg (Dostal et al. 1987b). At this time, no DEHP could be detected in dams plasma, but substantial amounts of MEHP were detected. Pups plasma had no detectable DEHP or MEHP. No other dose levels were tested in this study. Dostal et al. (1987b) noted that exposure to DEHP was associated with an increase in milk solids and lipids. Addition of 14C-DEHP to milk in vitro resulted in 94% of the... 

The associated report concluded, "These data illustrate the efficiency of the blood-brain barrier and the blood-testicular barrier in limiting the access and accumulation of this highly lipophilic substance into brain and testis. ... 

Surface-active substances — are electroactive or elec-troinactive substances capable to concentrate at the interfacial region between two phases. Surface-active substances accumulate at the electrode-electrolyte - interface due to -> adsorption on the electrode surface (see -> electrode surface area) or due to other sorts of chemical interactions with the electrode material (see - chemisorption) [i]. Surface-active substances capable to accumulate at the interface between two immiscible electrolyte solutions are frequently termed surfactants. Their surface activity derives from the amphiphilic structure (see amphiphilic compounds) of their molecules possessing hydrophilic and lipophilic moieties [ii]. 

Sulfur mustard is a strongly lipophilic substance that may accumulate in fatty tissues and has actually been detected at autopsy in a patient who had died 7 days post-exposure. Detailed data, as published by Drasch and colleagues (1987), are displayed in Table 50.6. 

For lipophilic substances this factor can be quite high, but theoretically, there will always be an equilibrium concentration, where no net uptake takes place. The factor is quite versatile as a simple parameter that describes the tendency of a substance to accumulate. 

Hydrophobic and lipophilic substances that tend to accumulate in sediment and biota should be monitored in these matrices for resource effective trend monitoring in order to ... 

Lipophilic substances such as fatty acids have also been found to accumulate in the myocardium and this has prompted a search for Tc agents which might replace Tl in heart imaging applications. However, the binding of Tc to 2-mercaptohexadecanoic acid and related sub-... 

The accumulation of toxic lipophilic substances from the enviromnent... 

Interactions of the accumulated lipophilic substances with the cytoplasmatic membranes and especially hydrophobic parts of the cell or cell membranes. Lipid-lipid interactions and interactions between proteins and lipids of the membrane structure (lipid bilayers, membrane-embedded proteins) are discussed. 

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