Relationship of specific granules to renin activity in the myocardium

In this study we have shown that sodium deprivation of rats increased the number of specific granules and renin activity in atria. Sodium loading and DOCA treatment were found to lower the number of granules and renin activity. Renin activity which is present in both atria and ventricles is not localized in specific granules, as shown by ultracentrifugation and immunocytochemistry. Although this renin activity was partially abolished by preincubation with specific antiserum, the present results do not rule out the possibility that the activity is due to cathepsin D.