Development of SHR hypertension and cardiac hypertrophy during prolonged beta blockade.

Spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats were treated with beta-adrenergic receptor inhibiting drugs (either propranolol or timolol) from conception until 12 weeks of age to determine if this therapy would alter the development of systemic hypertension or left ventricular hypertrophy. Therapy (propranolol or timolol, 500 mg/liter drinking water) was initiated with breeding parents and continued throughout the pregnancy, nursing, and postweaning periods. Although the heart rates of beta-adrenergic receptor inhibited WKY and SHR rats were consistently reduced with respect to their respective tap-water controls, this therapy did not alter body growth. Hemodynamic studies demonstrated reduced central venous pressure, cardiac index, and maximum acceleration of aortic flow in the beta-adrenergic inhibited rats. In spite of these findings, the arterial pressure of the treated rats and the degree of left ventricular hypertrophy of the SHR were unaltered by treatment. Thus, administration of the beta-adrenergic receptor blocking agents, propranolol or timolol, from conception through the developmental stage of SHR hypertension, failed to alter either the progressive rise in arterial pressure or the development of hypertensive vascular disease and left ventricular hypertrophy.