Tracheal relaxing effects and β 2 adrenoceptor selectivity of S1319, a novel sponge‐derived bronchodilator agent, in isolated guinea‐pig tissues

S1319 (4‐hydroxy‐7‐[1‐(1‐hydroxy‐2‐methylamino)ethyl]‐1,3‐benzothiazol‐2(3 H )‐one acetate), a novel non‐catecholamine β‐adrenoceptor agonist, has been compared with isoprenaline, salbutamol and formoterol for activity in vitro on a range of β‐adrenoceptor containing preparations from guinea‐pig. S1319, like isoprenaline, salbutamol and formoterol, relaxed preparations of guinea‐pig trachea (contracted by histamine) in a concentration‐dependent manner. The relaxing activity of S1319 appeared to be more potent than that of isoprenaline and salbutamol, and similar to that of formoterol (pD 2 values of 10.58±0.03 vs 7.60±0.01, 7.50±0.01 and 10.52±0.04, respectively), and was blocked by the β 2 ‐adrenoceptor selective antagonist (ICI 118,551). The intrinsic activity of S1319 was close to 1.0. In the β 1 ‐adrenoceptor containing preparations, guinea‐pig right and left atria, a monophasic inotropic response of S1319 was observed. The pD 2 value of S1319 for left atrial and right atrial inotropism was 6.70±0.15 and 7.81±0.01, respectively. The selectivity ratio (trachea/left atrial inotropism) of S1319, formoterol, salbutamol and isoprenaline was 8523, 284, 4.8 and 0.45, respectively. The relative selectivity ratio of S1319 was 18743, 1858 and 30 times greater than that of isoprenaline, salbutamol and formoterol, respectively. Relaxant responses of guinea‐pig trachea to S1319 declined rapidly when the agonist was washed from the tissues, with complete recovery within 30 min. The duration of action of S1319 was similar to that of isoprenaline and less than that of salbutamol and formoterol. In summary, S1319, a sponge‐derived β‐adrenoceptor agonist, is a potent and selective β 2 ‐adrenoceptor agonist with a short‐duration of action in isolated guinea‐pig tracheas.British Journal of Pharmacology (1999) 128 , 716–720; doi: 10.1038/sj.bjp.0702839