ABSTRACT

Madin-Darby canine kidney (MDCK) cells, an epithelial cell line originated from an unknown site of a dog kidney, have been very useful in studying the mechanisms concerning the osmoregulatory accumulation of these osmolytes. All of the transporters mentioned are regulated by medium tonicity, indicating that they are responsible for the osmoregulatory accumulation of osmolytes in the cells. The “direct expression” strategy was not successful for the taurine transporter even after screening more than 50 pools. The magnitude of the increase in the myoinositol (MI) transport and cell MI content depends on the solute used to increase the osmolality of the medium. To delineate the role of transcription in the increase of SMIT messenger RNA abundance observed in hypertonic MDCK cells, the transcription rate of the gene was measured in isolated nuclei collected from cells switched to hypertonic medium. The sequence similarity extends to other recently cloned members of the family.