Hexoprenaline: beta-adrenoreceptor selectivity in isolated tissues from the guinea-pig.

1. A catecholamine beta-adrenoreceptor agonist, hexoprenaline, was examined in vitro on five guinea-pig tissues and its potency relative to isoprenaline (as 100) obtained. 2. Hexoprenaline clearly delineated between those tissues classified as containing beta2-adrenoreceptors (trachea, hind limb blood vessels and uterus; relative potencies 219, 110 and 76 respectively) and those classified as containing beta1-adrenoreceptors (atria and ileum; relative potencies 3.3 and 1.0 respectively). 3. Hexoprenaline differed from some previously studied noncatecholamine beta-adrenoreceptor agonists in being only two-fold less potent, relative to isoprenaline, as a vasodilator in perfused hind limb than as a tracheal relaxant.