α 1 -Adrenergic Receptor Subtypes in Human Peripheral Blood Lymphocytes

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Abstract
—We investigated the expression of α 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 α 1 -adrenergic receptors (α 1A , α 1B , and α 1D ). RT-PCR amplified in peripheral blood lymphocytes a 348-bp α 1A -adrenergic receptor fragment, a 689-bp α 1B -adrenergic receptor fragment, and a 540-bp α 1D -adrenergic receptor fragment. Radioligand binding assay with [ 3 H]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 [ 3 H]prazosin binding to human peripheral blood lymphocytes was consistent with the labeling of α 1 -adrenergic receptors. Antibodies against α 1A -, α 1B -, and α 1D -receptor subtypes decreased [ 3 H]prazosin binding to a different extent. This indicates that human peripheral blood lymphocytes express the three α 1 -adrenergic receptor subtypes. Of the three different α 1 -adrenergic receptor subtypes, the α 1B is the most represented and the α 1D , the least. Future studies should clarify the functional relevance of α 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 α 1 -adrenergic receptors in cardiovascular disorders or for assessing responses to drug treatment on these receptors.

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