Evidence for the conversion of angiotensin I to angiotensin II by the coronary microcirculation.

Cardiac tissue from hamster neonates was transplanted into the hamster cheek pouch. After vascularization of the transplanted tissue the vessels were tested for their ability to convert angiotensin I (AI) to angiotensin II (AII). AI caused vasoconstriction of the coronary vessels which was reduced significantly by converting enzyme inhibitor and the AII antagonist (Sar1-Ala8) angiotensin II. It was concluded that the vessels of transplanted cardiac allografts convert AI to AII in a manner similar to that observed in the whole heart indicating that this procedure provides a good model for studying the microcirculation of the heart.