Effects of captopril and clonidine on resting and stress cardiac performance of left ventricle in spontaneously hypertensive rats

Captopril (Cap) 20 mg.kg-1.d-1 and clonidine (Clo) 300 micrograms.kg-1.d-1 were given po to SHR from their parents mating day to 24 wk of age, with untreated, age-matched SHR and WKY as controls. Stress cardiac function was assessed by the development of LVdp/dtmax in response to incremental pressure load (phenylephrine, Phe) and volume load (dextran, Dex). The slope of delta HR/delta MAP relationship curve was used as an index of baroceptor sensitivity. Results showed that both Cap and Clo caused decreases in BP in SHR. Cap not only reduced markedly the left ventricular mass/body weight (LVM/BW), (mg.g-1, 2.7 +/- 0.4 vs SHR 3.5 +/- 0.3, P < 0.01), but also normalized the LVdp/dtmax, -LVdp/dtmax, T value, and the stress cardiac function. Clo neither decreased the LVM/BW (mg.g-1, 3.4 +/- 0.5 vs SHR 3.5 +/- 0.3, P > 0.05), nor improved the resting and stress cardiac function. The results suggested that attenuation of the left ventricular hypertrophy (LVH) is beneficial not only to the resting but also stress cardiac performance.