Direct Actions of Urotensin II on the Heart

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Abstract
Urotensin II (UII) is a somatostatin-like peptide recently identified as a potent vasoconstrictor. In this study, we examined whether UII promotes cardiac remodeling through nonhemodynamic effects on the myocardium. In a rat model of heart failure after myocardial infarction (MI), increased UII peptide and UII receptor protein expression was observed in both infarct and noninfarct regions of the left ventricle compared with sham. Moreover, post-MI remodeling was associated with a significant 75% increase in UII receptor gene expression in the heart (P<0.05 versus sham controls), with this increase noted in both regions of the left ventricle. In vitro, UII (10−7 mol/L) stimulation of neonatal cardiac fibroblasts increased the level of mRNA transcripts for procollagens α1(I), α1(III), and fibronectin by 139±15% (P<0.01), 59±5% (P<0.05), and 141±14% (P<0.01), respectively, with a concomitant 23±2% increase in collagen peptide synthesis as determined by 3H-proline incorporation (P<0.01). UII had no effect on ...