Retinoid receptors tissues

A most important function of vitamin A is in the control of cell differentiation and mrnover. PsA-trans-retinoic acid and 9-cw-retinoic acid (Figure 45-1) regulate growth, development, and tissue differentiation they have different actions in different tissues. Like the steroid hormones and vitamin D, retinoic acid binds to nuclear receptors that bind to response elements of DNA and regulate the transcription of specific genes. There are two families of nuclear retinoid receptors the retinoic acid receptors (RARs) bind all-rrijw-retinoic acid or 9-c -retinoic acid, and the retinoid X receptors (RXRs) bind 9-cw-retinoic acid. 

Retinoid Hormones Retinoids are potent hormones that regulate the growth, survival, and differentiation of cells via nuclear retinoid receptors. The prohormone retinol is synthesized from vitamin A, primarily in liver (see Fig. 10-21), and many tissues convert retinol to the hormone retinoic acid (RA). 

All tissues are retinoid targets, as all cell types have at least one form of nuclear retinoid receptor. In adults, the most significant targets include cornea, skin, epithelia of the lungs and trachea, and the immune system. RA regulates the synthesis of proteins essential for growth or differentiation. Excessive vitamin A can cause birth defects, and pregnant women are advised not to use the retinoid creams that have been developed for treatment of severe acne. 

Cell extracts expressing recombinant retinoid receptors or cell or tissue extracts expressing endogenous levels of retinoid receptors (store as aliquots at -80°C). 

Retinoid Receptor Subtype Protein Levels in Various Cultured Cell, Tissue, and Tumor Extracts... 

Nonisotopic In Situ Hybridization for the Detection of Nuciear Retinoid Receptor Transcripts in Tissue Sections... 

More background information can be found in two books dedicated to ISH (11,12). Note that retinoid receptor or binding-protem transcript distribution may also be analyzed by whole-mount ISH of digoxigenm-labeled riboprobes, a method that is particularly informative at early stages of development and is described in Chapter 5 and in refs. 12 and 22, In Chapter 18, Xu and Lotan describe the use of digoxigenin-labeled RAR riboprobes for ISH of paraffin-embedded tissue sections. 

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