Hypotonic stress induces translocation of the osmolyte channel protein pICln in embryonic skate (Raja eglanteria) heart.

ABSTRACT

Volume expansion of cardiac cells from a wide variety of species stimulates the efflux of the beta-amino acid taurine through an osmolyte channel. Previous studies have suggested that the osmolyte channel in epithelial cells is a swelling-activated anion channel (pICln). In skate heart, a 37-kDa protein is present which is recognized by a specific antibody to a protein characterized in MDCK cells as pICln. This protein is present predominantly in the cytosol (only 10% in the membrane fraction) of heart incubated under isotonic conditions. After transfer to hypotonic medium (one-half osmolarity), the distribution of this protein is markedly altered and significant amounts of the protein are found in the membrane fraction. After hypotonic exposure, the amount 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 stimulated by hypotonic stress.