AJP - Cell Physiology, Vol 266, Issue 3 C676-C683, Copyright © 1994 by American Physiological Society

ARTICLES

Volume regulation in cultured cells derived from human retinal pigment epithelium

B. G. Kennedy
Department of Physiology, Northwest Center for Medical Education, Indiana University School of Medicine, Gary 46408.

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.

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