title: Increased myoendothelial gap junctions mediate the enhanced response to epoxyeicosatrienoic acid and acetylcholine in mesenteric arterial vessels of cirrhotic rats.
abstract: BACKGROUND
  Cirrhotic portal hypertension is characterized by mesenteric arterial vasodilation and hyporeactivity to vasoconstrictors.
  
  
  OBJECTIVE
  We evaluated the role of epoxyeicosatrienoic acid (EET) and of myoendothelial gap junctions (GJ) in the haemodynamic alterations of experimental cirrhosis.
  
  
  METHODS
  Thirty-five control rats and 35 rats with carbon tetrachloride (CCl(4))-induced cirrhosis were studied. Small resistance mesenteric arteries (diameter <350 μm) were connected to a pressure servo controller in a video-monitored perfusion system. Concentration-response curves to acetylcholine (ACh) were evaluated in mesenteric arteries pre-incubated with indomethacin, N(G)-nitro-L-arginine-methyl-ester and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one before and after the epoxygenase inhibitor miconazole or 18α-glycyrrhetinic acid (18α-GA) (GJ inhibitor). EC(50) was calculated. Concentration-response curves to 11,12-EET were also evaluated. mRNA and protein expression of connexins (Cxs) in the mesenteric arteries was evaluated by real-time PCR and immunohistochemistry.
  
  
  RESULTS
  The ACh response was increased in cirrhotic rats (EC(50): -6.55±0.10 vs. -6.01±0.10 log[M]; P<0.01) and was blunted by miconazole only in cirrhotic animals. 18α-GA blunted the response to ACh more in cirrhotic than that in control rats (P<0.05). Concentration-response curves to 11,12-EET showed an increased endothelium-dependent vasodilating response in cirrhotic rats (P<0.05); the BK(Ca) inhibitor Iberiotoxin (25 nM) blocked the response in normal rats but not in cirrhotic rats, while 18α-GA blunted the response in cirrhotic rats but not in control rats. An increased mRNA and protein expression of Cx40 and Cx43 in cirrhotic arteries was detected (P<0.05).
  
  
  CONCLUSIONS
  The increased nitric oxide/PGI(2)-independent vasodilation of mesenteric arterial circulation in cirrhosis is because of, at least in part, hyperreactivity to 11,12-EET through an increased expression of myoendothelial GJs.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Padua, Padua, Italy. massimo.bolognesi@unipd.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Bolognesi
authors.forename: Francesca
authors.initials: F
authors.lastname: Zampieri
authors.forename: Marco
authors.initials: M
authors.lastname: Di Pascoli
authors.forename: Alberto
authors.initials: A
authors.lastname: Verardo
authors.forename: Cristian
authors.initials: C
authors.lastname: Turato
authors.forename: Fiorella
authors.initials: F
authors.lastname: Calabrese
authors.forename: Francesca
authors.initials: F
authors.lastname: Lunardi
authors.forename: Patrizia
authors.initials: P
authors.lastname: Pontisso
authors.forename: Paolo
authors.initials: P
authors.lastname: Angeli
authors.forename: Carlo
authors.initials: C
authors.lastname: Merkel
authors.forename: Angelo
authors.initials: A
authors.lastname: Gatta
authors.forename: David
authors.initials: D
authors.lastname: Sacerdoti
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D002251:Carbon Tetrachloride; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism; D006975:Hypertension, Portal / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D007150:Immunohistochemistry; D008106:Liver Cirrhosis, Experimental / Q000139:chemically induced / Q000150:complications / Q000378:metabolism / Q000503:physiopathology*; D016015:Logistic Models; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D017711:Nonlinear Dynamics; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D000071756:Soluble Guanylyl Cyclase; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D017630:Connexins; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014665:Vasodilator Agents; D009569:Nitric Oxide; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; D002251:Carbon Tetrachloride; D011464:Epoprostenol; D019001:Nitric Oxide Synthase; D011451:Prostaglandin-Endoperoxide Synthases; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D015126:8,11,14-Eicosatrienoic Acid; D000109:Acetylcholine