The antihypertensive peptides, Val-Pro-Pro and Ile-Pro-Pro, were successfully detected in the aorta of spontaneously hypertensive rats after orally administering these peptides by a guanidine-thiocyanate treatment to prevent proteolysis. Cy3-labeled versions of both peptides were localized in the endothelial cells of arterial vessels in the rats. The accumulation of both peptides in the endothelial cells suggested in vivo inhibitory activity of the angiotensin I-converting enzyme.
