Antihypertensive effects of labetalol in three types of hypertensive models of rats

Abstract

Effects on blood pressure and heart rate of labetalol, a new beta-adrenoceptor blocking agent with α-blocking action were studied in conscious hypertensive rats (SHR, DOCA-hypertensive rats and renal hypertensive rats (RHR)). Labetalol with two asymmetric carbon atoms consists of an equal proportion of two racemates. In SHR, prevention of the development of hypertension was noted after 1.5 weeks of chronic oral administration of labetalol 25, 50 and 100 mg/kg/day, while bradycardia occurred beginning with the day of administration. Thus, the prevention of the development of hypertension appeared much earlier than in the case of the other β-blockers. Antihypertensive effects and bradycardia were also noted in DOCA hypertensive rats and RHR after oral administration of Labetalol 10, 30 and 100 mg/kg/day for six days. In DOCA hypertensive rats, the antihypertensive effect was more pronounced than in the RHR. These findings are in contrast to those obtained with other β-blockers. Other β-blockers produced antihypertensive effects only in SHR. It is concluded that not only the β-blocking action, but also the α-blocking action of labetalol plays an important role in the antihypertensive effects of labetalol.