Role of angiotensin in autoregulation of cerebral blood flow.
The presence of the renin-angiotensin system (RAS) in extrarenal tissues, namely the vascular wall and brain tissue, is well established. The availability of effective blocking agents, converting-enzyme inhibitors, has made it possible to further elucidate important functions of the extrarenal RAS. We have found that the angiotensin converting-enzyme inhibitor captopril shifts the limits of cerebral blood flow autoregulation to lower blood pressure levels in normotensive and in spontaneously hypertensive rats. This effect may explain our finding of a remarkable preservation of cerebral blood flow, despite significant blood pressure reduction, in patients with chronic heart failure. We suggest that the effect of angiotensin converting-enzyme inhibition on autoregulation of cerebral blood flow is mediated by a dilatation of larger cerebral arteries, which results from inhibition of the vascular tone normally maintained by locally produced angiotensin II.
Paulson
O B
OB
Department of Neurology, Rigshospitalet (University Hospital), Copenhagen, Denmark.
Waldemar
G
G
Andersen
A R
AR
Barry
D I
DI
Pedersen
E V
EV
Schmidt
J F
JF
Vorstrup
S
S
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D002216:Captopril / Q000494:pharmacology / Q000627:therapeutic use; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006333:Heart Failure / Q000188:drug therapy / Q000503:physiopathology; D006706:Homeostasis / Q000187:drug effects; D006801:Humans; D012084:Renin-Angiotensin System / Q000187:drug effects
D000804:Angiotensin II; D002216:Captopril