Differentiation of metabolic adrenoceptors

1 Cardiovascular and metabolic responses to intravenous infusion of isoprenaline were measured in fasted, anaesthetized cats. 2 Isoprenaline (0.2 mug kg-1 min-1 for 15 min) decreased diastolic blood pressure and increased heart rate, blood glucose, blood lactate and plasma free fatty acids. 3 Oxprenolol (0.5 mg/kg) antagonized all cardiovascular and metabolic effects of isoprenaline non-selectively. 4 Para-oxprenolol (0.25 mg/kg) and practolol (4 mg/kg) antagonized the effects of isoprenaline on heart rate and free fatty acids selectively. 5 H 35/25 ((I-(4-methylphenyl)-2-isopropyl aminopropanol) hydrochloride, 3 mg/kg) antagonized the effects of isoprenaline on blood pressure, glucose and lactate selectively. 6 It is concluded that metabolic adrenoceptors are differentiated into subtypes similar to those mediating cardiostimulation and vasodilatation.