MOLECULAR PHARMACOLOGY, 44:70-75 Human a2-Adrenergic Receptor Subtype Distribution: Widespread and Subtype-Selective Expression of a2Cl 0, a2C4, and a2C2 mRNA in Multiple Tissues

At present, molecular cloning and pharmacological studies have delineated three human a2-adrenergic receptor (a2AR) subtypes, a2Cl 0, a2C4, and a2C2. Assignment of the a2AR subtypes to specific functions has been limited by an unclear definition of tissue a2AR expression outside of the central nervous system. It has been suggested that a2C4 expression is confined to the brain, that a2C2 expression is only in the liver and kidney, and that there is nearly ubiquitous expression of a2Cl 0. However, this is based on studies of a limited number of rat tissues or on studies using non-species-specific approaches. Therefore, to define a2Cl 0, a2C4, and a2C2 tissue expression, we used re-verse transcription of total RNA isolated from 20 human tissues, followed by amplification of a2AR cDNA using the polymerase chain reaction. This technique provided two advantages: high sensitivity and, with the use of subtype-specific oligonucleotid