title: The effects of cardioselective and non-selective beta-adrenoceptor blockade on the hypokalaemic and cardiovascular responses to adrenomedullary hormones in man.
abstract: Adrenaline was infused intravenously in nine normal volunteers to plasma concentrations similar to those found after myocardial infarction. This study was undertaken on three occasions after 5 days' treatment with placebo or the beta-adrenoceptor antagonists, atenolol or timolol. Adrenaline increased the systolic pressure by 11 mmHg, decreased the diastolic pressure by 14 mmHg, and increased the heart rate by 7 beats/min. These changes were prevented by atenolol. However, after timolol the diastolic pressure rose (+19 mmHg) and heart rate fell (-8 beats/min). Adrenaline caused the corrected QT interval (QTc) to lengthen (0.36 +/- 0.02 s to 0.41 +/- 0.06 s). No significant changes were found in the QTc when subjects were pretreated with atenolol or timolol. The serum potassium fell from 4.06 to 3.22 mmol/l after adrenaline. Serum potassium fell to a lesser extent to 3.67 mmol/l after atenolol and actually increased to 4.25 mmol/l after timolol. Adrenaline-mediated hypokalaemia appears to result from the stimulation of a beta 2-adrenoceptor linked to membrane Na+/K+-ATPase causing potassium influx.
mesh_terms: D000328:Adult; D001262:Atenolol / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D004837:Epinephrine / Q000097:blood*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007008:Hypokalemia / Q000209:etiology; D008297:Male; D009203:Myocardial Infarction / Q000097:blood / Q000150:complications; D011188:Potassium / Q000097:blood*; D011412:Propanolamines / Q000494:pharmacology*; D013999:Timolol / Q000494:pharmacology*
chemical_list: D011412:Propanolamines; D001262:Atenolol; D013999:Timolol; D011188:Potassium; D004837:Epinephrine