Impulse conduction and gap junctional remodelling by endothelin-1 in cultured neonatal rat ventricular myocytes.
Endothelin-1 (ET-1) is an important contributor to ventricular hypertrophy and failure, which are associated with arrhythmogenesis and sudden death. To elucidate the mechanism(s) underlying the arrhythmogenic effects of ET-1 we tested the hypothesis that long-term (24 hrs) exposure to ET-1 impairs impulse conduction in cultures of neonatal rat ventricular myocytes (NRVM). NRVM were seeded on micro-electrode-arrays (MEAs, Multi Channel Systems, Reutlingen, Germany) and exposed to 50 nM ET-1 for 24 hrs. Hypertrophy was assessed by morphological and molecular methods. Consecutive recordings of paced activation times from the same cultures were conducted at baseline and after 3, 6 and 24 hrs, and activation maps for each time period constructed. Gap junctional Cx43 expression was assessed using Western blot and confocal microscopy of immunofluorescence staining using anti-Cx43 antibodies. ET-1 caused hypertrophy as indicated by a 70% increase in mRNA for atrial natriuretic peptide (P < 0.05), and increased cell areas (P < 0.05) compared to control. ET-1 also caused a time-dependent decrease in conduction velocity that was evident after 3 hrs of exposure to ET-1, and was augmented at 24 hrs, compared to controls (P < 0.01). ET-1 increased total Cx43 protein by approximately 40% (P < 0.05) without affecting non- phosphorylated Cx43 (NP-Cx43) protein expression. Quantitative confocal microscopy showed a approximately 30% decrease in the Cx43 immunofluorescence per field in the ET-1 group (P < 0.05) and a reduced field stain intensity (P < 0.05), compared to controls. ET-1-induced hypertrophy was accompanied by reduction in conduction velocity and gap junctional remodelling. The reduction in conduction velocity may play a role in ET-1 induced susceptibility to arrhythmogenesis.
Rappaport Family Institute for Research in the Medical Sciences, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
Y
Y
Reisner
G
G
Meiry
N
N
Zeevi-Levin
D Y
DY
Barac
I
I
Reiter
Z
Z
Abassi
N
N
Ziv
S
S
Kostin
J
J
Schaper
M R
MR
Rosen
O
O
Binah
D000818:Animals; D000831:Animals, Newborn; D006332:Cardiomegaly / Q000473:pathology / Q000503:physiopathology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism; D019332:Endothelin-1 / Q000494:pharmacology*; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism*; D006329:Heart Conduction System / Q000187:drug effects* / Q000503:physiopathology; D006352:Heart Ventricles / Q000166:cytology* / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley
D018031:Connexin 43; D019332:Endothelin-1