Purpose To determine the nature of the relationship between cell volume and mRNA expression of pICln, a chloride channel regulatory protein associated with the myo-mositol efflux pathway in cultured bovine lens epithelial cells (BLECs). Methods Two distinct experimental approaches were designed to delineate the circumstances that alter mRNA expression of pic,. For rapid cellular shrinkage, BLECs were maintained at confluence in physiologic medium (Phys, 257 mosm), subsequently transferred to sodium hypertonic medium (NaCl, 480 mosm) For rapid cellular swelling, cells were switched from NaCl to Phys ±niflumic acid (NA) or tamoxifen (TX), drugs which exacerbate swelling because they block osmolyte efflux from cell to medium. For gradual cellular swelling, BLECs were switched from Phys to 40 mM galactose medium (Gal) or NaCl to NaCl + Gal. Results. Upon raising medium tomcity (rapid cell shrinkage), BLECs upregulate the expression of pl mRNA. With lowering of medium osmolality (rapid cell swelling), BLECs moderately downregulate expression of pl mRNA, however, addition of NA or TX severely downregulated expression of plc,n mRNA Gal exposure (gradual cell swelling) showed no change in expression of pla mRNA relative to corresponding control Conclusions. These data suggest a converse relationship exists between plan mRNA expression and cell volume reduction or expansion Hypertonicity prompts BLECs to rapidly shrink, concentrating internal ions and causing active accumulation ofosmofytes. Ensuing upregulation of pL mRNA suggests a preparatory response via an unknown signaling mechanism that senses the loss of cell volume (or, alternatively, the impending need to efflux osmolytes from cell to medium as their levels increase). Hypotonicity prompts rapid cell swelling, normally eliciting osmolyte efflux. Succeeding downregulabon of pICln mRNA suggests an inhibitory response via a mechanism that senses the eain in cell volume for. alternatively, alleviation of the need to efflux osmolytes).
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - 1 Dec 1997|