1. The possible inhibitory effect of des-angiotensin I substrate on the renin-substrate reaction was studied. For this purpose rat angiotensinogen was purified 50-fold from plasma of nephrectomized rats. Des-angiotensin substrate was prepared from the purified angiotensinogen preparation by reaction with immobilized hog renin (coupled to Sepharose).
2. In kinetic experiments it was found that des-angiotensin I substrate in concentrations of 0·225 and 0·45 μmol/l has no influence on the reaction between rat renin and rat angiotensinogen.