title: Volume regulation in cultured cells derived from human retinal pigment epithelium.
abstract: To characterize volume regulatory mechanisms, unidirectional Rb+ efflux and influx, unidirectional Cl- influx, and cell volume were measured in cultured human retinal pigment epithelium (HRPE). The HRPE was found to be capable of both regulatory volume increase (RVI), in response to a hypertonic challenge, and regulatory volume decrease (RVD), in response to a hypotonic challenge. Bumetanide-sensitive Rb+ influx increased almost threefold on incubation in a hypertonic (390 mosmol/kgH2O) medium. Bumetanide-insensitive Rb+ influx was activated by hypotonic (190 mosmol/kgH2O) challenge as well as by treatment with N-ethylmaleimide (NEM). Exposure to hypotonic media also activated unidirectional Cl- influx and unidirectional Rb+ efflux. Both the RVD and hypotonically activated Rb+ efflux were inhibited by the K(+)-channel blocker barium. On the other hand, hypotonically activated Rb+ influx was increased by barium treatment. In sum, the HRPE exhibits volume-sensitive transport mechanisms over a range of volumes from 190 to 390 mosmol/kgH2O. Cultured HRPE possess hypertonically activated Na-K-Cl cotransport, hypotonically activated K-Cl cotransport, and a barium-inhibitable hypotonically activated K+ efflux pathway.
authors.affiliation: Department of Physiology, Northwest Center for Medical Education, Indiana University School of Medicine, Gary 46408.
authors.forename: B G
authors.initials: BG
authors.lastname: Kennedy
mesh_terms: D017609:Barium Compounds / Q000494:pharmacology; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology; D003470:Culture Media; D005033:Ethylmaleimide / Q000494:pharmacology; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D008027:Light; D009994:Osmolar Concentration; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism*; D012413:Rubidium / Q000493:pharmacokinetics; D012542:Scattering, Radiation
chemical_list: D017609:Barium Compounds; D002712:Chlorides; D003470:Culture Media; D007038:Hypotonic Solutions; C024986:barium chloride; D002034:Bumetanide; D012413:Rubidium; D005033:Ethylmaleimide