Selectivity selective tissue binding

The endothelin receptor subtypes show differences in their signal transduction, ligand binding and tissue distribution. The ETA receptor is isopeptide-selective and binds ET-1 and ET-2 with the same and ET-3 with 70-100-fold lower affinity. The ETB receptor binds all three isoforms with the same affinity. 

Mechanism of Action Modulates differentiation and proliferation of epithelial tissue, binds selectively to retinoic acid receptors. TherapeutkEffect Restores normal differentiation of the epidermis and promotes reduction of epidermal inflammation. Pharmacokinetics Minimal systemic absorption occurs through the skin. Binding to plasma proteins is greater than 99%. Metabolism is in the skin and liver. Elimination occurs through the fecal and renal pathways. Half-life 18 hr. 

Steroid receptors are highly specific macromolecules found in central regulatory organs (e.g., pituitary, hypothalamus), in various end-point target tissues (e.g., uterus, vagina, prostate), and in lower concentrations in the brain, liver, kidney, ovary, and many other organs. Steroid hormones exhibit remarkable tissue selectivity when binding to these... 

Drug Distribution. After administration, a drug may be distributed either generally or selectively in the body. The distribution pattern depends on many factors, including the pattern and time-course of blood (low, diffusion of drugs into tissues, binding of drugs to plasma proteins and cellular compartments, and elimination kinetics and mechanisms. 

Salmi, M., Granfors, K., Leirsalo-Rcpo, M., Hamalainen, M., MacDermott, R, Leino, R, Havia, T. and Jalkanen, S. (1992). Selective endothelial binding of interleukin-2-dependent human T cell lines derived from different tissues. Proc. Natl. Acad. Sci. USA 89, 11436-11440. 

Many proteins in the blood and in various tissues bind steroids selectively. While the binding affinities of these proteins for steroids are lower than those of the steroid... 

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