Endothelin-a receptor in rat skeletal muscle microvasculature.
Although the effect of endothelin-1 (ET-1) on vascular tone has been studied extensively at the arterial/arteriolar level, little is known about the direct effect of ET-1 at the level of the capillary. Using intravital microscopy, we determined capillary red blood cell velocity and arteriolar diameter responses to ET-1, ET(A)-receptor blocker BQ-123, and ET(B)-receptor blocker BQ-788 applied locally on capillaries in rat extensor digitorum longus (EDL) muscle. Using immunohistochemistry, we examined capillaries in this muscle and microvascular endothelial cells isolated from this muscle for immunoreactivity with ET(A)-receptor antibody. ET-1 (10(-9) to 10(-5) M in micropipette) caused quick reductions (i.e., within several seconds), whereas BQ-123 (10(-8) to 10(-4) M) and BQ-788 (10(-6) and 10(-4) M) caused quick increases, in both velocity and diameter. Capillaries and endothelial cells showed ET(A)-receptor immunoreactivity. We conclude that the microvasculature of the rat EDL muscle is sensitive to ET-1 and its receptor blockers and that the ET(A) receptor may be present in the capillary wall of this muscle, including the endothelium.
Mitchell
Debra
D
Departmente of Pharmacology and Toxicology, The University of Western Ontario, London, Ontario, N6A 5C1, Canada.
Bihari
Aurelia
A
Sandig
Martin
M
Tyml
Karel
K
D000818:Animals; D001783:Blood Flow Velocity; D002196:Capillaries / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D007150:Immunohistochemistry; D008297:Male; D008833:Microcirculation / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000096:biosynthesis*; D013997:Time Factors
D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin