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 μmol/ml) and anti-integrin β₁ specific antibody (10 μg/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 β₁ blocking antibody effectively inhibited the increase in ³H-leucine incorporation and release of ANP (p < 0.05). Following anti-integrin-β₁- 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-β₁-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.