Changes in cochlear blood flow due to intra-arterial infusions of angiotensin II (3-8) (angiotensin IV) in guinea pigs.
The effects of a newly discovered form of angiotensin, angiotensin IV (ANGIV), on cochlear blood flow (CBF) have been investigated utilizing the laser Doppler flowmetry (LDF) technique. Two specific questions were addressed: What are the effects of anterior inferior cerebellar artery infusions (AICA) of ANGIV on CBF and do angiotensin fragments other than ANGIV influence CBF in mature male and female guinea pigs. Infusions of ANGIV, and C-terminal shortened fragments were accomplished via micropipette into the AICA and changes in CBF were observed using LDF. The results demonstrated that 10 and 100 pmol/min doses of ANGIV increased CBF 22% and 75% (n = 6; P < 0.01) from baseline, respectively, with little change in mean arterial blood pressure (MAP). Pretreatment with the ANGIV antagonist divalanal-ANGIV (1 nmole/min) blocked increases in CBF due to infusions of 100 pmol/min of ANGIV. The infusion of the C-terminal shortened fragment ANGIV(1-5) and saline had no significant effect on either CBF or MAP. These results provide the evidence for a new subtype of the angiotensin receptor and indicate the likely role of circulating hormones in blood flow regulation in the inner ear.
Coleman
J K
JK
Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor 48109-0506, USA.
Lee
J I
JI
Miller
J M
JM
Nuttall
A L
AL
D000595:Amino Acid Sequence; D000804:Angiotensin II / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D003051:Cochlea / Q000098:blood supply / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D007261:Infusions, Intra-Arterial; D017078:Laser-Doppler Flowmetry; D008297:Male; D008969:Molecular Sequence Data; D012039:Regional Blood Flow / Q000187:drug effects
C114974:divalanal-angiotensin IV; D000804:Angiotensin II; C012877:angiotensin II, des-Asp(1)-des-Arg(2)-Ile(5)-