HYPOTONIC STRESS INDUCES TRANSLOCATION OF THE OSMOLYTE CHANNEL PROTEIN PICI(N) IN EMBRYONIC SKATE (RAJA-EGLANTERIA) HEART

Volume expansion of cardiac cells from a wide variety of species stimu lates the efflux of the beta-amino acid taurine through an osmolyte ch annel. Previous studies have suggested that the osmolyte channel in ep ithelial cells is a swelling-activated anion channel (pICl(n)). In ska te heart, a 37-kDB protein is present which is recognized by a specifi c antibody to a protein charac terized in MDCK cells as pICl(n). This protein is present predominantly in the cytosol (only 10% in the membr ane fraction) of heart incubated under isotonic conditions. After tran sfer to hypotonic medium (one-half osmolarity), the distribution of th is protein is markedly altered and significant amounts of the protein are found in the membrane fraction. After hypotonic exposure, the amou nt of the protein in the membrane fraction rises to 38 +/- 11% (range 18-53, n=3). The translocation to the membrane fraction suggests that this protein may play a role in the taurine efflux in this tissue stim ulated by hypotonic stress. (C) 1997 WiIey-Liss, Inc.