Given an abstract from a research paper, your task is to identify and label relationships between chemical compounds and genes mentioned in the abstract.

The relationship type must be one of ['DOWNREGULATOR', 'SUBSTRATE', 'INDIRECT-REGULATOR', 'PART-OF', 'MODULATOR-ACTIVATOR', 'REGULATOR', 'INHIBITOR', 'COFACTOR', 'UPREGULATOR', 'ACTIVATOR', 'ANTAGONIST', 'NOT', 'INDIRECT-DOWNREGULATOR', 'SUBSTRATE_PRODUCT-OF', 'INDIRECT-UPREGULATOR', 'AGONIST', 'PRODUCT-OF', 'MODULATOR', 'DIRECT-REGULATOR', 'UNDEFINED', 'AGONIST-INHIBITOR', 'AGONIST-ACTIVATOR', 'MODULATOR-INHIBITOR'].

Please format your output as a JSON array. Each entry in the array should express a single relation, formatted as ["<Entity_A>", "<RELATION_A_B>", "<Entity_B>"]. If no relations can be found, please output an empty JSON array [].

Abstract:

Characterization of human recombinant alpha (2A) -adrenoceptors expressed in Chinese hamster lung cells using extracellular acidification rate changes. 1. Human alpha (2A) -adrenoceptors heterologously expressed in Chinese hamster lung (CHL) fibroblasts have been characterized pharmacologically using a cytosensor microphysiometer to measure ligand-induced extracellular acidification rate changes. 2. In untransfected CHL cells, noradrenaline had no effect at concentrations up to 100 microM. In alpha (2A) -adrenoceptor transfected cells the rank order of agonist potency was A-54741 (mean pEC (50) =8.96) >dexmedetomidine (8.88) >UK-14304 (8.42) >B-HT 920 (7.05) >noradrenaline (6.92). A-54741, UK-14304 and noradrenaline had the same maximum response while dexmedetomidine and B-HT 920 behaved as partial agonists. 3. The selective alpha (2) -adrenoceptor ligand rauwolscine antagonized acidification rate changes with an affinity independent of the agonist used; the affinity (mean pK (B)) against noradrenaline was 8.43. 4. The selective alpha (1) -adrenoceptor ligands prazosin and doxazosin (each 3 microM) had no effect on noradrenaline responses. 5. Acidification rate changes induced by each agonist were abolished by pre-treatment of cells with pertussis toxin. 6. These data suggest that agonist-induced acidification rate responses in CHL cells transfected with the human alpha (2A) -adrenoceptor are mediated exclusively by the recombinant protein, via pertussis toxin sensitive G (i/o) proteins.
[["noradrenaline", "REGULATOR", "alpha (2) -adrenoceptor"], ["A-54741", "AGONIST", "alpha (2A) -adrenoceptor"], ["doxazosin", "DIRECT-REGULATOR", "alpha (1) -adrenoceptor"], ["rauwolscine", "DIRECT-REGULATOR", "alpha (2) -adrenoceptor"], ["prazosin", "DIRECT-REGULATOR", "alpha (1) -adrenoceptor"]]