Force-independent expression of c-fos mRNA by endothelin-1 in rat intact small mesenteric arteries.
OBJECTIVE
Wall stress-independent signalling pathways were studied for endothelin-1 (ET-1)-induced c-fos expression in rat intact mesenteric small arteries.


METHODS
Arteries were kept unmounted in Krebs buffer, equilibrated for 1 h and stimulated with vasoactive substances for 15-60 min. The c-fos mRNA expression was determined by real-time polymerase chain reaction.


RESULTS
Stimulation with fetal bovine serum (FBS), phorbol 12-myristate 13-acetate (PMA) and ET-1 caused about a doubling of c-fos mRNA. The ET-1-induced c-fos expression was steady (15-60 min) and was inhibited by the inhibitor of the ET(A) receptor, BQ-123. Platelet-derived growth factor-B, angiotensin II and U46619 did not cause increased c-fos mRNA levels. The broad specificity inhibitor staurosporine inhibited the response to ET-1, but inhibitors of Rho-A kinase and phosphatidylinositol 3-kinase had no effect. However, inhibitors to tyrosine kinases, the MAP kinases [extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun amino-terminal kinase, p38], and to conventional protein kinase C showed no inhibition. Consistent with these findings, ET-1 did not cause activation of ERK1/2, a finding also seen in vessels held under pressure. In contrast, ET-1-induced c-fos expression was inhibited by the calcium chelator BAPTA, suggesting a role for intracellular calcium. This possibility was supported by the finding that raising the extracellular K(+) concentration caused increased expression of c-fos in a concentration-dependent manner.


CONCLUSIONS
The results suggest that in the absence of wall stress, ET-1 is able to induce increased expression of c-fos independent of traditional growth pathways, such as MAP kinase. The mechanism appears to be calcium-dependent.
Buus
C L
CL
Department of Pharmacology, University of Aarhus, Aarhus, Denmark.
Kristensen
H B
HB
Bakker
E N T P
EN
Eskildsen-Helmond
Y E G
YE
Mulvany
M J
MJ
D000818:Animals; D002118:Calcium / Q000378:metabolism; D019332:Endothelin-1 / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000378:metabolism; D015870:Gene Expression; D016762:Genes, fos / Q000235:genetics*; D017403:In Situ Hybridization / Q000379:methods; D008638:Mesenteric Arteries / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics; D009924:Organ Culture Techniques; D010766:Phosphorylation; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D017208:Rats, Wistar; D044022:Receptor, Endothelin A / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D019311:Staurosporine / Q000378:metabolism
D019332:Endothelin-1; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019311:Staurosporine; D002118:Calcium