α1-adrenergic receptor subtypes in human peripheral blood lymphocytes

We investigated the expression of alpha(1)-adrenergic receptor subtypes in intact human peripheral blood lymphocytes using reverse transcription-polymerase chain reaction (RT-PCR) and radioligand binding assay techniques combined with antibodies against the three subtypes of alpha(1)-adrenergic receptors (alpha(1A), alpha(1B), and alpha(1D)). RT-PCR amplified in peripheral blood lymphocytes a 348-bp alpha(1A)-adrenergic receptor fragment, a 689-bp alpha(1B)-adrenergic receptor fragment, and a 540-bp alpha(1D)-adrenergic receptor fragment. Radioligand binding assay with [H-3]prazosin as radioligand revealed a high-affinity binding with a dissociation constant value of 0.65 +/- 0.05 nmol/L and a maximum density of binding sites of 175.3 +/- 20.5 fmol/10(6) cells. The pharmacological profile of [H-3]prazosin binding to human peripheral blood lymphocytes was consistent with the labeling of alpha(1)-adrenergic receptors. Antibodies against alpha(1A)-, alpha(1B)-, and alpha(1D)-receptor subtypes decreased [H-3]prazosin binding to a different extent. This indicates that human peripheral blood lymphocytes express the three alpha(1)-adrenergic receptor subtypes. Of the three different alpha(1)-adrenergic receptor subtypes, the alpha(1B) is the most represented and the alpha(1D), the least. Future studies should clarify the functional relevance of alpha(1)-adrenergic receptors expressed by peripheral blood lymphocytes. The identification of these sites may represent a step for evaluating whether they represent a marker of alpha(1)-adrenergic receptors in cardiovascular disorders or for assessing responses to drug treatment on these receptors.