Association of intrinsic pI(Cln) with volume-activated Cl- current and volume regulation in a native epithelial cell

We investigated the relationship between pI(Cln), the volume-activated Cl- current, and volume regulation in native bovine nonpigmented ciliary epithe lial (NPCE) cells. Immunofluorescence studies demonstrated the presence of pI(Cln) protein in the NPCE cells. Exposure to hypotonic solution activated a Cl- current and induced regulatory volume decrease (RVD) in freshly isol ated bovine NPCE cells. Three antisense oligonucleotides complementary to h uman pI(Cln) mRNA were used in the experiments. The antisense oligonucleoti des were taken up by the cells in a dose-dependent manner. The antisense ol igonucleotides, designed to be complementary to the initiation codon region of the human pI(Cln) mRNA, "knocked down" the pI(Cln) protein immuno fluor escence, delayed the activation of volume-activated Cl- current, diminished the value of the current, and reduced the ability of the cells to volume r egulate. We conclude that pI(Cln) is involved in the activation pathway of the volume-activated Cl- current and RVD following hypotonic swelling.