K⁺ fluxes mediated by Na⁺‐K⁺‐Cl⁻ cotransport and Na⁺‐K⁺‐ATPase pumps in renal tubule cell lines transformed by wild‐type and temperature‐sensitive strains of simian virus 40

Abstract

The relative contributions of Na(+)-K(+)-ATPase pumps and Na(+)-K(+)-Cl- cotransport to total rubidium (Rb+) influx into primary cultures of renal tubule cells (PC.RC) and cells transformed either with the wild-type or a temperature-sensitive mutant of the simian virus 40 (SV40), were measured under various growth conditions. The Na(+)-K(+)-ATPase-mediated component represented 74% and 44-48% of total Rb+ influx into PC.RC and SV40-transformed cells, respectively. Proliferating transformed cells showed substantial ouabain-resistant bumetanide-sensitive (Or-Bs) Rb+ influx (41-45% of total) which indicated the presence of a Na(+)-K(+)-Cl- cotransport. The Or-Bs component of Rb+ influx was greatly reduced when temperature-sensitive transformed renal cells (RC.SVtsA58) grown in Petri dishes or on permeable filters were shifted from the permissive (33 degrees C) to the restrictive temperature (39.5 degrees C) to arrest cell growth. The ouabain-sensitive Rb+ influx mediated by the Na(+)-K(+)-ATPase, the total and amiloride-sensitive Na+ uptakes were not modified following inhibition of cell proliferation. A similar fall in the Or-Bs influx was obtained when renal tubule cells transformed by the wild-type SV40 (RC.SV) were incubated with the K+ channel blocker, tetraethylammonium (TEA) ion, which we had previously shown to arrest cell growth without affecting cell viability (Teulon et al.: J. Cell. Physiol., 151:113-125, 1992). Reinitiation of cell growth by removal of TEA or return to 33 degrees C of the temperature-sensitive cells restored the Or-Bs component of Rb influx. Taken together, these results indicate that the Na(+)-K(+)-Cl- cotransport activity is critically dependent on cell growth conditions.

Rat lung alveolar type II cell line maintains sodium transport characteristics of primary culture

“…This bumetanide-sensitive component of wRb+ influx required the presence of external Na+, K' and C1-in the incubation medium; (2) "Na+ influx was partly inhibited by bumetanide. The presence of Na+-K+-Cl-cotransport has been claimed to be the result of SV40induced transformation and to be related to rate of cell growth (Vandewalle et al, 1993). In our studies, several lines of evidence suggest that Na+, K', C1-expression in SV40-T2 cells is an intrinsic characteristic of these cells unrelated to cell proliferation status: (1) serum deprivation which induced growth arrest did not modify Na+-K+-Cl-cotransport activity in SV40-T2 cells; and (2) in the case of alveolar type I1 cells in primary culture, the presence of Na+-K+-Cl-cotransport was also evidenced in the first days in culture (Clerici et al, 1995) while no proliferation could be detected (Clement et al, 1990) hiloride-sensitive Na+ channels in SV4O-T2 cells Matalon et al (1991) demonstrated the presence of amiloride-sensitive sodium channels in the apical membranes of alveolar type I1 cells.…”