title: Role of calcineurin in insulin-like growth factor-1-induced hypertrophy of cultured adult rat ventricular myocytes.
abstract: The present study examined the role of calcineurin in insulin-like growth factor (IGF)-1-induced hypertrophy in primary cultures of adult rat ventricular myocytes (ARVM), prepared from the ventricles of 14-16-week-old male Sprague-Dawley rats. The effects of several humoral factors, including phenylephrine, angiotensin II, endothelin-1, IGF-1 and interleukin-6, on the morphology of ARVM were studied. Myocyte surface area was significantly increased by IGF-1 (2,268 +/- 571 to 3,018 +/- 836 microm2, p < 0.01), but not by other humoral factors. This hypertrophic effect of IGF-1 was blocked by genistein (tyrosine kinase inhibitor), PD98059 (MEK inhibitor). These findings suggest that IGF-1 produces ARVM hypertrophy by a tyrosine kinase-MEK mediated pathway as has been reported in neonatal cardiomyocytes. IGF-1-mediated ARVM hypertrophy was also attenuated by cyclosporine A (calcineurin inhibitor), and staurosporine and chelerythrine (protein kinase C inhibitors). IGF-1 markedly increased calcineurin activity (8.7 +/- 1.2 to 98.0 +/- 54.3 pmol x h(-1) mg(-1), p < 0.01), and this activation was completely blocked by pre-treatment with cyclosporine A (8.5 +/- 11.4pmol x h(-1) x mg(-1), p < 0.01) and chelerythrine (2.3 +/- 2.7 pmol x h(-1) mg(-1), p < 0.01). It appears that IGF-1 activates calcineurin by a protein kinase C-dependent pathway. Increased mRNA expression of atrial natriuretic factor by IGF-1 was inhibited by cyclosporine A (p < 0.01). The findings indicate that IGF-1 induces ARVM hypertrophy by protein kinase C and calcineurin-related mechanisms. The fact that elevated calcineurin activity and induced atrial natriuretic factor mRNA expression by IGF-1 were blocked by cyclosporine A further supports the hypothesis that calcineurin is critically involved in IGF-1-induced ARVM hypertrophy.
authors.affiliation: The First Department of Internal Medicine, Yamagata University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Miyashita
authors.forename: Y
authors.initials: Y
authors.lastname: Takeishi
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: S
authors.initials: S
authors.lastname: Kato
authors.forename: I
authors.initials: I
authors.lastname: Kubota
authors.forename: H
authors.initials: H
authors.lastname: Tomoike
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000235:genetics; D019703:Calcineurin / Q000502:physiology*; D006332:Cardiomegaly / Q000139:chemically induced* / Q000473:pathology; D048429:Cell Size; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006352:Heart Ventricles / Q000187:drug effects / Q000473:pathology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D009320:Atrial Natriuretic Factor; D011493:Protein Kinase C; D019703:Calcineurin