Mechanical Stretch-Induced Hypertrophy of Neonatal Rat Ventricular Myocytes is Mediated by β1-Integrin-Microtubule Signaling Pathways

BACKGROUND: Mechanical stress plays a crucial role in tissue morphogenesis and remodeling. These processes depend in part on force transmission mediated through integrins and the cytoskeleton. METHODS: Ventricular myocytes isolated from neonatal Sprague-Dawley rats (NRVMs) were exposed to persistent centrifugal force stretch for 12 or 24 h. The NRVMs were exposed to colchicine (4 micromol/ml) and anti-integrin beta1 specific antibody (10 microg/ml). Cell viability was assessed by MTT assay and lactate dehydrogenase (LDH) activity. Incorporation of 3H-leucine, and atrial natriuretic peptide (ANP) and angiotensin II (Ang II) levels were assessed. Pixel intensity and distribution of the microtubule were estimated from laser scanning confocal images. RESULTS: Changes in LDH release and the MTT assay showed that 180 rpm. centrifugal force had minimal effect on the viability and number of NRVMs. Mechanical stretch significantly increased 3H-leucine incorporation into cardiomyocytes. Anti-integrin beta1 blocking antibody effectively inhibited the increase in 3H-leucine incorporation and release of ANP (p < 0.05). Following anti-integrin-beta1-blocking antibody, the pixel intensity of the microtubule image was decreased after both12 and 24 h stretch, this was similar to the effect of colchicine. Both treatments also inhibited the secretion of Ang II induced by stretch (p < 0.05). CONCLUSIONS: Anti-integrin-beta1-blocking antibody and colchicine had similar effects, partly inhibiting the stretch-induced increase in microtubule polymerization and the secretion of Ang II in hypertrophic cardiac myocytes.