A new orally active hypotensive peptide, N-(dibenzyloxyphosphinoyl)-L-alanyl-L-prolyl-L-proline (PAPP).

The antihypertensive effects and mechanisms of a newly developed orally active tripeptide, N-(dibenzyloxyphosphinoyl)-L-alanyl-L-prolyl-L-proline (PAPP), were investigated. When PAPP (1-30 mg/kg orally) was administered to spontaneously hypertensive rats (SHR), systolic blood pressure (SBP) reached a maximum reduction after 8 h and this effect lasted over 24 h. In two-kidney, one clip hypertensive rats (2KIC rats) and DOCA-salt hypertensive rats, PAPP also reduced SBP. In normotensive Wistar rats, however, PAPP did not have a hypotensive effect. PAPP showed low toxicity in Sprague-Dawley rats. The depressor response to bradykinin (BK) was potentiated, but the pressor response to angiotensin I (ANG I) was not inhibited by PAPP. PAPP significantly relaxed isolated SHR aortic strips treated with KC or norepinephrine. Angiotensin converting enzyme (ACE) inhibition by PAPP was relatively low in vivo and in vitro.