Regulatory volume decrease by cultured renal cells.

Volume regulatory responses of OK cells (a continuous epithelioid cell line from opossum kidney) are examined by electronic cell sizing and measurements of intracellular pH in cell suspensions. In response to a 40% reduction in osmolality, the cells swell and then subsequently shrink toward their starting volume. This regulatory volume decrease (RVD) is reduced by replacement of Cl- in the medium with acetate. Replacement of Cl- with NO3- accelerates the RVD. The RVD response is inhibited by 1 mM quinine or 100 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) in the medium. The inhibitory effect of 100 microM DIDS (but not 1 mM quinine) is altered by replacement of Cl- by NO3- in the medium. Hypotonic challenge does not induce a DIDS-sensitive net flux of acid-base equivalents. Addition of (9 microM) valinomycin also inhibits the RVD response. It is suggested that the RVD response of OK cells involves activation of separate K+ and Cl- channels.