| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
In the heart, the expressions of several types of prostanoid receptors have been reported. However, their roles in cardiac hypertrophy in vivo remain unknown. We intended to clarify the roles of these receptors in pressure overload-induced cardiac hypertrophy using mice lacking each of their receptors. We employed a model of pressure overload-induced cardiac hypertrophy produced by banding of the transverse aorta in female mice. In wild-type mice subjected to the banding, cardiac hypertrophy developed during the observation period of 8 weeks. In mice lacking the prostaglandin (PG) I_2 receptor (IP^<-/-> mice), however, cardiac hypertrophy and cardiomyocyte hypertrophy were significantly greater than in wild-type mice at 2 and 4 weeks but not at 8 weeks, while there was no such augmentation in mice lacking the prostanoid receptors other than IP. In addition, cardiac fibrosis observed in wild-type hearts was augmented in IP^<-/-> hearts, which persisted for up to 8 weeks. In IP^<-/-> hearts, the expression level of mRNA for atrial natriuretic peptide, a representative marker of cardiac hypertrophy, was significantly higher than in wild-type hearts. In vitro, cicaprost, an IP agonist, reduced platelet derived growth factor-induced proliferation of wild-type non cardiomyocytes, although it could not inhibit cardiotrophin-1-induced hypertrophy of cardiomyocytes. Accordingly, cicaprost increased cAMP concentratiion efficiently in noncardiomyocytes. The results indicate that IP plays a suppressive role in the development of pressure overload-induced cardiac hypertrophy via the inhibition of both cardiomyocyte hypertrophy and cardiac fibrosis, both effects having been suggested as originating from the action on non-cardiomyocytes rather than that on cardiomyocytes.
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