Abstract
The hemodynamic effects of propranolol, pindolol and practolol were investigated in conscious spontaneously hypertensive rats (SHR). Mean blood pressure (MBP), heart rate (HR) and cardiac output (CO) were measured and total peripheral resistance (TPR) was calculated. CO was determined by the modified dye dilution method using an arterio-venous shunt between the left carotid artery and the right jugular vein. Intraperitoneal administration of propranolol (5 mg/kg), pindolol (0.1 mg/kg) or practolol (50 mg/kg) caused a sustained antihypertensive effect of a similar degree. The antihypertensive effect of propranolol (20-30 mmHg, 0.5-8 hr) was attributed to an early decrease of CO (0.5-4 hr) followed by a reduction of TPR (6-8 hr), while that of pindolol or practolol (30-50 mmHg, 0.5-8 hr; 30 mmHg, 2-8 hr) was apparently related to a reduction of TPR with a CO increment. HR decreased with propranolol but increased with pindolol, while only slight changes were observed with practolol. Antihypertensive effects of propranolol, pindolol or practolol were associated with characteristic hemodynamic changes.
