TRPV4 is a Ca2+-permeable channel and is sensitive to osmotic and mechanical stimuli as well as thermal stimuli.TRPV4 protein expresses widely in various kinds of tissues.In the cardiac myocytes, TRPV4 has been detected only at the mRNA level and there were few reports about the subcellular location of TRPV4 protein.The purpose of the present study was to investigate the expression profile of TRPV4 protein in cultured neonatal rat ventricular myocytes.Using Western blots, immunofluorescence, confocal microscopy and immuno-electron microscopy, we have shown that TRPV4 protein is located not only in the cytoplasm and the plasma membrane, but also in the nucleus of the myocytes.Furthermore, cardiac myocytes responded to hypotonic stimulation by translocating TRPV4 protein from the nucleus to the cytoplasm and membrane.The significance and mechanism concerning the distribution and translocation for TRPV4 protein in cultured neonatal cardiac myocytes remain to be clarified.