Mechanical stretch-induced hypertrophy of neonatal rat ventricular myocytes is mediated by beta(1)-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.