The A3 adenosine receptor is the unique adenosine receptor which facilitates release of allergic mediators in mast cells.

摘要: Mast cells release the mediators of immediate hypersensitivity reaction. Adenosine is known to modulate this process, but receptor responsible for not classical A1 or A2 adenosine receptors. This study was undertaken determine whether unique (AR) previously postulated in a cultured mast cell line (RBL-2H3 cells) recently cloned A3AR. The receptors were quantitated by agonist 125I-labeled APNEA (aminophenylethyladenosine), an A3AR agonist, which yielded Bmax and Kd values 826 fmol/mg protein 34 nM, respectively. A variety analogs competed 125I-APNEA binding sites with following potency series: (R)-phenylisopropyladenosine = 5'-N-ethylcarboxamide > (S)-phenylisopropyladenosine. relatively insensitive xanthine amine congener (XAC, 1 microM), selective antagonist A1AR. Functionally, activation these stimulated production inositol 1,4,5-triphosphate, leading increase level intracellular Ca2+. Furthermore, while alone produced little secretory response RBL-2H3 cells, it enhanced antigen-induced secretion 2-2.5-fold. Northern blotting studies using poly(A+) RNA from detected two transcripts 2.0 3.5 kilobases, hybridized cDNA A2AR probes. These data indicate that AR potentiates antigen exclusively