[Prevention of the development of genetic hypertension by MK 421 in the SHR]

MK 421, 25 mg/kg, administered daily by gavage to young spontaneously hypertensive rats (SHRs) from their 4th to 15th weeks of age almost completely inhibited genetic hypertension development. Since heart rate and cardiac index were not drug affected, prevention of genetic hypertension development was solely related to an early, potent and long-lasting limitation of the progressive increase in peripheral resistance which normally develops in SHRs during ageing. MK 421 slightly enhanced vascular responsiveness to exogenous norepinephrine and angiotensin II and reduced myocardial hypertrophy. Plasma renin concentration was increased. MK 421 slightly reduced body growth but did not affect fluid intake, urinary volume and urinary ADH, demonstrating that no water or salt retention developed. Finally, MK 421's preventive effects against genetic hypertension development persisted up to 10 weeks after treatment discontinuation.