Endothelin receptor function in mesenteric veins from deoxycorticosterone acetate salt-hypertensive rats.
OBJECTIVE
To identify the receptors by which endothelin-1 (ET-1) increases venomotor tone in hypertension.


METHODS
Vascular reactivity to ET-1 and the selective endothelin receptor subtype B (ET(B)) agonist, sarafotoxin 6c (S6c), was studied in mesenteric blood vessels from deoxycorticosterone acetate (DOCA-salt) hypertensive and normotensive control rats. The diameter of small (< or = 280 microm) mesenteric arteries and veins was monitored in vitro using computer-assisted video microscopy. Contractions of mesenteric arteries (< or= 250 microm diameter) were also studied, using a myograph. ET-1 mRNA levels were measured in mesenteric arteries and veins using real-time RT-PCR techniques.


RESULTS
ET-1-induced contractions were reduced in arteries of DOCA-salt hypertensive rats compared with those of normotensive control rats; S6c produced negligible contractions in arteries from both groups. ET-1 concentration-responses curves in arteries measured using video microscopy or a myograph were similar. ET-1 and S6c caused veins to contract, and there were no differences between responses to these agonists in tissues from DOCA-salt hypertensive rats or normotensive control rats. Studies using ET(A) and ET(B) receptor antagonists indicated that ET-1-induced venoconstriction was mediated by ET(A) receptors. Potassium chloride concentration-response curves were similar in arteries and veins from normotensive control rats and DOCA-salt hypertensive rats. ET-1 mRNA levels in DOCA-salt hypertensive rat arteries or veins were not different from those in normotensive control rat arteries and veins.


CONCLUSIONS
These data indicate that ET-1 reactivity is maintained in mesenteric veins, but not arteries, in DOCA-salt hypertension. Therefore, the sustained increase in venomotor tone mediated by ET(A) receptors that is known to occur in vivo in DOCA-salt hypertensive rats is not caused by direct venoconstriction.
Johnson
Ronald J
RJ
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, USA.
Fink
Gregory D
GD
Watts
Stephanie W
SW
Galligan
James J
JJ
D000818:Animals; D003900:Desoxycorticosterone / Q000633:toxicity; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D006973:Hypertension / Q000209:etiology / Q000235:genetics / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000503:physiopathology; D008642:Mesenteric Veins / Q000187:drug effects / Q000503:physiopathology*; D009842:Oligopeptides / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000502:physiology*; D012982:Sodium, Dietary / Q000633:toxicity; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology
D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D009842:Oligopeptides; D010880:Piperidines; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D012982:Sodium, Dietary; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6; C087220:BQ 610; D003900:Desoxycorticosterone; C086539:BQ 788; D011189:Potassium Chloride