Tissue distribution pattern

Phytoestrogens may elicit their biological effects by binding to estrogen receptors (ERs). Until recently, only a single ER isoform, ERa, had been identified however, a second receptor termed ERp has also been identified (Enmark et al, 1997, 1999 Saunders et al, 2000, 2001). It has been shown that the ERs have different intracellular and tissue distribution patterns and are responsible for different biological effects (see Table 5.1). A number of spliced variants of both ERa and ERp have also been identified (Inoue et al, 2000 Ogawa et al, 1998 Vladusic et al, 1998). 

Wu, X., et al. Structural and functional characteristics and tissue distribution pattern of rat OCTN1, an organic cation transporter, cloned from placenta. Biochim. Biophys. Acta 2000, 1466, 315-327. 

Wu X, Huang W, Prasad PD, et al. Functional characteristics and tissue distribution pattern of organic cation transporter 2 (OCTN2), an organic cation/camitine transporter. J Pharmacol Exp Ther 1999 290 1482-1492. 

The bioavailability of pure as opposed to soil-adsorbed benzene was conducted in adult male rats (Turkall et al. 1988). Animals were gavaged with an aqueous suspension of 14C-benzene alone, or adsorbed to clay or sandy soil. Two hours after exposure, stomach tissue contained the highest amount of radioactivity, followed by fat in all treatment groups. No differences in tissue distribution patterns were detected for the three treatments. 

Based on uptake and metabolism studies, the accumulation and tissue distribution patterns of PCDEs have been suggested to be similar to those of PCBs [63,109]. According to uptake studies of PCDEs in trout and Atlantic salmon, the uptake of PCDEs in fish is similar to that of PCBs [83,109]. When the uptake of mono through tetraCDEs was studied in brook trout, it was observed that the uptake of PCDEs was rapid ranging from 2.4 pg day"1 to 48.9 pg day"1 and did not reach a steady state during a seven day exposure [83]. The accumulation coefficients of PCDEs 28, 66, and 99 were 0.31,0.33, and 0.36 in Atlantic salmon, respectively [109]. 

Several cannabinoid receptor ligands have been radiolabelled with tritium, and these have been used both to determine the CB 1 and CB2 receptor affinities of unlabelled cannabinoids in displacement assays and to establish the tissue distribution patterns of these receptors (reviewed in Howlett et al. 2002 Pertwee 1999a). As indicated in Tables 1,2 and 3, some of these compounds bind more readily to CBi or to CB2 receptors, whilst the others bind more or less equally well to both these... 

Two other novel approaches have recently been reported in the field of ER ligand discovery. The potential of compounds as pathway-selective ligands and antiinflammatory agents was studied by the use of NFKB-driven reporter assays [64], A second relatively recent focus for ER-directed drug discovery is related to the fact that there are two subtypes of this receptor, ERa and ER 1, which derive from two separate genes [65, 66], Stimulated by the specific tissue distribution pattern of these two related receptors, research to find ER subtype-selective modulators for the treatment... 

It can be speculated that the true cholinergic agents exert an action analogous to that of ACh because of considerable structural similarities. A cationic head a proper distance from a degradable polar moiety is the primary structural requirement for ACh-like activity. The remaining parts of the molecule are modifiers and thus may be viewed as of secondary importance. They have pronounced effects, however, on such parameters as degree of activity, duration of action, tissue distribution patterns, and metabolism. 

The original FGFs, FGF-1 and -2, which have been commercially available as purified or recombinant proteins for a number of years, are by far the best studied in terms of their actions on cells of the nervous system. Less is known about the newer FGF family members, which are only recently becoming characterized in terms of their expression and their tissue distribution patterns. 

Tissue distribution patterns are well-defined and reflect the unique chemistry of these substitution-inert complexes. 

Repletion of retinol-deficient rats can also be effectively achieved by the intravenous injection of retinol dispersed in a 20% Tween 40 solution (Smith et al., 1980 Fig. 4). Such an injection produces a rapid, dose-related increase in the serum concentration of RBP. The changes in serum RBP levels seen after the injection of retinol in a 20% Tween 40 solution closely resembled those previously seen after the injection of vitamin A (retinyl esters) in association with lymph chylomicrons. However, the amount of retinol required to stimulate the secretion of a given amount of RBP from the liver was about two to three times that required when retinol (retinyl esters) was injected in chylomicrons. As discussed by Smith et al. (1980), this quantitative difference is probably due to differences in the tissue distribution pattern of retinol when injected in the Tween 40 solution, compared to its administration in the form of chylomicrons. 

Peptides, in comparison to proteins, present advantages such as low toxicity and immunogenicity. Their small size improves pharmacokinetic characteristics and tissue distribution patterns, helps to obtain a more efficient conjugation to the imaging agent, and simplifies synthesis and production (Chen and Conti, 2010 Marr et al., 2011). Low bioavailability, which is related to the susceptibility of the peptides to protease activity, to the poor absorption of peptides by tissues, and also to the short circulation half-life in the blood stream, is the major limitation of these ligands (Ibraheem et al., 2014 Yu et al., 2014). 

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