Dose-related inhibitory effects of the beta-adrenoceptor blocking drugs carteolol and propranolol on cardiac hypertrophy in spontaneously hypertensive rats.

The inhibitory effect of two kinds of beta-adrenoceptor blocking drugs [propranolol: 1-100 mg/kg per day; carteolol: 0.3-30 mg/kg per day] on the development of cardiac hypertrophy was studied in young spontaneously hypertensive rats (SHR: 4 weeks old). Though neither propranolol or carteolol given for 6 weeks reduced the development of hypertension in SHR, both drugs did reduce the increase in the heart weight/body weight ratio in a dose-dependent manner. This potency of carteolol was about 300 times greater than that of propranolol. The potency of carteolol with regard to the reduction in the myocardial protein/DNA ratio was about 300 times greater than that of propranolol. The beta-blocking potency, estimated from the area under the dose-response curve (beta-blocking action) of carteolol, was also 300 times greater than that of propranolol and correlated well with the extent of the structural changes in the heart. Thus, the possibility that the degree of beta-blocking potency may strongly relate to structural changes in the heart of young SHR has to be given consideration.