Enhancement of Rho/Rho-kinase system in regulation of vascular smooth muscle contraction in tachycardia-induced heart failure.
OBJECTIVE
The Rho/Rho-kinase system regulates Ca(2+) sensitivity in vascular smooth muscle. A new drug, Y-27632, specifically inhibits Rho-kinase and hence decreases the phosphorylation of myosin light chain, thus reducing contraction. Here, we compare the effects of Y-27632 and nifedipine on the vasoconstrictor response of the femoral artery in heart failure.


METHODS
Heart failure (HF) was produced by chronic rapid RV pacing (250 bpm, 28 days, six dogs). Indo1-AM was loaded into endothelium-denuded femoral artery segments for measuring intracellular [Ca(2+)]. Tension and changes in intracellular [Ca(2+)] [the change in the ratio (418 nm/468 nm) of Indo1 fluorescence (F(ratio))] were simultaneously measured in Krebs-Ringer solution.


RESULTS
In HF: (i) norepinephrine (10 microM) produced greater tension (784+/-52 g/cm(2)) than in control (502+/-64 g/cm(2)) despite a similar increase in F(ratio), indicating increased Ca(2+) sensitivity in vascular smooth muscle; (ii) nifedipine attenuated this enhanced response by only a maximum of 27% at 1 micromol/l with a 56% reduction in F(ratio); (iii) Y-27632 attenuated it by a maximum of 80% at 100 micromol/l without a significant change in F(ratio); (iv) RhoA protein and mRNA expression levels in the femoral artery were up-regulated by +110% and +56%, respectively, while those of Rho-kinase were unchanged.


CONCLUSIONS
The Ca(2+)-sensitizing mechanism involving the Rho/Rho-kinase system may be deeply involved in the enhanced arterial vasoconstriction seen in HF. Since Y-27632 attenuated this response in small arteries, it shows potential as a novel, potent vasodilator for the treatment of HF.
Hisaoka
T
T
The Department of Biomedical Regulation/Cardiovascular Medicine (Second Department of Internal Medicine), Yamaguchi University School of Medicine, 1-1-1 Minami-kogushi, Ube, 755-8505, Yamaguchi, Japan.
Yano
M
M
Ohkusa
T
T
Suetsugu
M
M
Ono
K
K
Kohno
M
M
Yamada
J
J
Kobayashi
S
S
Kohno
M
M
Matsuzaki
M
M
D000577:Amides / Q000494:pharmacology*; D000704:Analysis of Variance; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002304:Cardiac Pacing, Artificial; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005263:Femoral Artery; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology*; D015151:Immunoblotting / Q000379:methods; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000503:physiopathology*; D009543:Nifedipine / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
D000577:Amides; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D000804:Angiotensin II; C108830:Y 27632; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D009543:Nifedipine; D002118:Calcium