Endothelin-1 causes luminal constrictions in rat cochlear veins.
Serum levels of the vasoconstrictor endothelin-1 (ET-1) increase in ischemia and systemic hypertension. We examined the effects of ET-1 on the cochlear microvasculature. Blood vessels were cast with methacrylate in adult male Wistar Kyoto rats, 10 min after intravenous injection of ET-1 (1.0 microg/kg); control animals received saline. Systemic blood pressure was recorded continuously. ET-1 increased the average systolic pressure by 18% and average diastolic pressure by 22% (P < 0.01). Scanning electron microscopy of cast vessels showed multiple circumscribed luminal constrictions on: (1) postcapillary venules; (2) collecting veins; (3) where collecting veins merged with the spiral modiolar vein; (4) on the spiral modiolar vein itself. Circumscribed constrictions in arteries were not observed. In ET-1 injected animals focal contractions of collecting veins reduced luminal width by 13.4% +/- 2.9 (P < 0.01). In control rats, constrictions on venous casts were minimal and constrictions on arteries were not observed. The present study shows that ET-1 is involved in local control of cochlear blood flow in that it focally contracts cochlear veins. It is suggested that this might be due to the high affinity of ET-1 receptors and/or the large number of ET-1 receptors on contractile cells in venous walls.
Franz
P
P
Department of Otorhinolaryngology, University of Vienna, Austria.
Aharinejad
S
S
Miksovsky
A
A
Schraufnagel
D E
DE
Larson
E K
EK
Marks
S C
SC
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003051:Cochlea / Q000098:blood supply* / Q000187:drug effects*; D016319:Corrosion Casting; D019332:Endothelin-1 / Q000494:pharmacology*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D051381:Rats; D011921:Rats, Inbred WKY; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects*; D014680:Veins / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
D019332:Endothelin-1; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin