OBJECTIVETo investigate the influence of mechanical stretch on the expression of myosin heavy chain (MHC) mRNA in cardiomyocyte subjected to ischemia and hypoxia.

METHODSMechanical stretch model of in vitro cultured cardiomyocyte was established for the study. The cells were processed by non-sugar hypoxic stimuli to simulate postburn ischemic and/or hypoxic injuries. The cells were then divided into normal control (N), 10% stretch (S), ischemic and hypoxic culture (IHC), 10% stretch with ischemia and hypoxia (SIHC) groups. The changes in MHC mRNA expression were observed at 1, 3, 6 and 12 post treatment hours (PTHs) by RT-PCR and were statistically analyzed with gel image analysis software.

RESULTSThe expression of both alpha and beta MHC mRNA increased in 10% stretch group, especially of beta MHC mRNA (P < 0.01). The transformation of alpha MHC mRNA to beta MHC mRNA was accelerated in IHC group, and alpha MHC mRNA expression was decreased at 12 PTH. The expression of beta MHC mRNA was increased after ischemia and hypoxia, peaked at 6 PTH, and decreased thereafter (P < 0.05). The transformation of alpha MHC mRNA to beta MHC mRNA was more obvious in SIHC group, and which was intensified along with the elapse of stimulation time. The expression of both alpha and beta MHC mRNA were down-regulated at 12 PTH (P < 0.05).

CONCLUSIONDown regulation of MHC mRNA expression by ischemia and hypoxia could be aggravated by mechanical stretch, indicating that mechanical stretch might be a possible cause for cardiac dysfunction.