Cerebrovascular reactivity to angiotensin and angiotensin-converting enzyme activity in cerebrospinal fluid.
The purpose of the present study was to test the vasomotor effect of angiotensin I (A I) and angiotensin II (A II) in feline cerebral arteries and to examine the presence of angiotensin converting enzyme (ACE) activity in the vessel wall and cerebrospinal fluid (CSF). A II (10(-8) -10(-5) M) induced concentration-dependent contractions of feline pial arteries (resting diameter, 98-286 microns) in situ with a maximum of 34% at 10(-4) M A II. A I produced dose-related contractions being approximately 20 times less potent than A II. The action of A I was significantly attenuated by the ACE inhibitor captopril (10(-5) M). These findings demonstrate the presence of ACE activity in the vessel wall and/or its surroundings. ACE activity was also found in feline CSF sampled from the cisterna cerebellomedullaris. Bradykinin (BK) was broken down and A I converted to A II by CSF, both effects being inhibited by captopril. This was demonstrated using bioassay and high-performance liquid chromatography. Considering the present and previous studies we conclude that the presence of ACE in the vessel wall and CSF is necessary for the conversion of A I to A II. Although ACE in CSF is able to degrade BK it appears not to be important for the metabolism of BK acting from the perivascular side of pial arteries in situ.
Whalley
E T
ET
Department of Physiology, University of Munich, F.R.G.
Wahl
M
M
D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001920:Bradykinin / Q000378:metabolism; D002216:Captopril / Q000494:pharmacology; D002415:Cats; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D008297:Male; D010296:Parietal Lobe / Q000098:blood supply / Q000187:drug effects / Q000502:physiology; D007703:Peptidyl-Dipeptidase A / Q000134:cerebrospinal fluid*; D014661:Vasoconstriction / Q000187:drug effects
D000804:Angiotensin II; D002216:Captopril; D007703:Peptidyl-Dipeptidase A; D001920:Bradykinin