<p><b>OBJECTIVE</b>
Phosphorylation of
myosin light chain (MLC) is one of the most important steps for
vascular smooth muscle contraction and
Rho-kinase is involved in this process. We investigated the
role of
Rho-kinase in a porcine
coronary artery spasm model with
interleukin-1beta .</p><p><b>
METHODS </b>Segments of left
coronary artery adventitia were surrounded by
normal saline (n = 8) or IL-1beta
agarose microne (n = 8) for 2 weeks. Vasospastic responses to intracoronary
serotonin or
histamine then studied at the saline or IL-1beta-treated site. The
Rho-kinase mRNA expression in the treated site was measured by
reverse transcription -
polymerase chain reaction analysis (RT-PCR). The extent of
phosphorylation of
myosin -binding subunit of
myosin phosphates (MBS, one of the major
substrates of
Rho-kinase ) were quantified by
Western blot analysis .</p><p><b>RESULTS</b>Intracoronary
serotonin or
histamine repeatedly induced
coronary artery spasm and coronary arterial
stenosis was evidenced at IL-1beta-treated site. Expression of
Rho-kinase mRNA in IL-1beta-treated site was significantly increased compared to saline treated site (98.20% +/- 7.66% vs. 63.70% +/- 4.26%, P < 0.05).
Western blot analysis showed that during the
serotonin -induced contractions the extent of
phosphorylation of MBS was also significantly increased in the
spastic site (25,485 +/- 4745 vs. 6510 +/- 779, P < 0.05).</p><p><b>CONCLUSION</b>
Rho-kinase upregulation at the
spastic site and increased
phosphorylation of
myosin -binding subunit of
myosin phosphates are key players in inducing
vascular smooth muscle hypercontraction in this porcine model.</p>