Expression of multiple alpha 2-adrenergic receptor messenger RNA species in rat tissues.

We used a human platelet alpha 2-adrenergic receptor probe to study the tissue distribution and messenger RNA (mRNA) forms of the rat alpha 2-adrenergic receptor. Under stringent conditions of hybridization and washing, we detected an mRNA species of 3.8 kb. The abundance of this form follows the order spleen, kidney, brain stem and cortex, and skeletal muscle and lung and is consistent with the reported abundance and tissue distribution of the alpha 2 receptor activity. A 3.0 kb mRNA form was also detected in cerebral cortex and brain stem and a 4.1 kb mRNA form was observed in kidney under less stringent hybridization conditions. The tissue distribution of the 3.0 kb form is different from that of alpha 1- and beta-adrenergic receptors and the D2 dopaminergic receptor. The mRNA analysis combined with Southern blot analysis of rat and human genomic DNA indicate that: 1) in addition to a 3.8 kb rat alpha 2-adrenergic receptor transcript, there are other mRNA forms in the rat that do not correspond to previously described adrenergic receptor mRNA species and 2) more than one alpha 2-adrenergic receptor gene in the rat is expressed in a tissue-specific manner.