MYOCARDIAL AND PLASMA RENIN-ANGIOTENSINOGEN DYNAMICS DURING PRESSURE-INDUCED CARDIAC-HYPERTROPHY

Plasma and left ventricular (LV) renin and angiotensinogen concentrati ons were assessed in a rat model of pressure-overload cardiac hypertro phy to determine if myocardial levels remained proportional to plasma levels over time. Three days after subdiaphragmatic aortic constrictio n (AC), LV hypertrophy was evident and renin concentrations in both pl asma and LV, although not significantly elevated, were positively corr elated with relative cardiac mass. After 42 days AC, LV hypertrophy re mained, plasma and LV renin and angiotensinogen levels were not differ ent from shams, and there was no correlation between renin and relativ e cardiac mass. Furthermore, LV renin and angiotensinogen concentratio ns remained at similar to 25 and 4%, respectively, of those in plasma throughout the experiment. Myocytes from 3-day AC and sham-treated rat s contained little renin as did LV from 48-h anephric rats. Incubation s using calculated concentrations of myocardial interstitial renin and angiotensinogen revealed significant angiotensin I generation. These data suggest that LV renin in this model varies directly with plasma r enin, is confined to the interstitial space, and can generate signific ant intramyocardial angiotensin I.