Mechanotransduction protein phosphorylation in rat neonatal myocytes is time and interval dependent

Cell adaptation and remodeling in response to mechanical stress begins with mechanosensing at focal adhesion sites. Our goal was to investigate both activation and deactivation of protein phosphorylation over time in rat neonatal ventricular myocytes (NRVM) in response to mechanical strain in order to test the hypothesis that there is a refractory period during which the response to mechanical strain is diminished. Our assays are site‐specific phosphorylation of paxillin and focal adhesion kinase (FAK). We cultured NRVM on fibronectin‐coated silicone surfaces and rapidly applied a strain of 10% that was either maintained over time or followed by a second strain of 10%. For a single strain phosphorylation levels of pY 397 ‐FAK increased between 5 min and 30 min (n=4, p<0.04), whereas phosphorylation of pY 31 ‐paxillin site peaked at 15 min and decreased by 30 min (n=3, p<0.05). In order to study the refractory period in NRVM, we varied the times and intervals between two strains both of 10% at 5 + 5 min or 15 + 15 min. There was no further response of pY 397 ‐FAK phosphorylation (n=4, p>0.07) for a second strain 5 min after the first, i.e. 10 min after the start. However, the second strain at 15 + 15 min significantly increased pY 397 ‐FAK phosphorylation (n=4, p<0.03). In conclusion, we suggest that mechano‐transduction in cardiomyocytes does have a refractory period. (Funded by AHA Predoctoral Fellowship 0415064Z, HL 62426).