α1-Adrenergic Receptor Subtypes in Human Peripheral Blood Lymphocytes

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Abstract
—We investigated the expression of α1-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 α1-adrenergic receptors (α1A, α1B, and α1D). RT-PCR amplified in peripheral blood lymphocytes a 348-bp α1A-adrenergic receptor fragment, a 689-bp α1B-adrenergic receptor fragment, and a 540-bp α1D-adrenergic receptor fragment. Radioligand binding assay with [3H]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/106cells. The pharmacological profile of [3H]prazosin binding to human peripheral blood lymphocytes was consistent with the labeling of α1-adrenergic receptors. Antibodies against α1A-, α1B-, and α1D-receptor subtypes decreased [3H]prazosin binding to a different extent. This indicates that human peripheral blood lymphocytes express the three α1-adrenergic receptor subtypes. Of the three different α1-adrenergic receptor subtypes, the α1Bis the most represented and the α1D, the least. Future studies should clarify the functional relevance of α1-adrenergic receptors expressed by peripheral blood lymphocytes. The identification of these sites may represent a step for evaluating whether they represent a marker of α1-adrenergic receptors in cardiovascular disorders or for assessing responses to drug treatment on these receptors.

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