Local ACE versus systemic ACE...

Initially, inhibition of systemic ACE was considered to be the most important result of ACE inhibitor therapy. This causes vasodilation and leads to consequent reduction in blood pressure.
However, opinions are changing and systemic ACE-inhibition is now considered to be only a small part of what really happens. Now it is realised that inhibiting ACE on a local level is of more significance^2,3.

The role of local ACE in heart failure

During the development of heart failure, before systemic or serum ACE is strongly activated, powerful changes occur in a number of tissues which are the result of the activation of tissue or local ACE.
This part was not well understood when ACE inhibitors were first used to treat heart failure and consequently widely ignored. Most vets have concentrated on the systemic action, assuming that ACE inhibitors only reduce flow resistance by opening blood vessels.

The importance of local ACE

It has now become clearer that various tissues become involved early on in ongoing heart failure and undergo degenerative changes, which are responsible for most of the problems seen in heart failure.
Angiotensin II produced at a local level by local ACE is directly involved in markedly changing the functional architecture of a number of tissues, most notably in the key organs of heart, blood vessel walls and kidney.