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

The relative contributions of Na + ‐ + ‐pumps and Na + ‐ + ‐ − contransport 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 + ‐ + ‐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 Na + ‐ + ‐ − contransport. The Or‐Bs component of Rb + influx was greatly reduced when temperature‐sensitive transformed renal cells (RC.SV ts A 58 ) grown in Petri dishes or on permeable filters were shifted from the permissive (33°C) to the restrictive temperature (39.5°C) to arrest cell growth. The ouabain‐sensitive Rb + influx mediated by the Na + ‐ + ‐, 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°C of the temperature‐sensitive cells restored the Or‐Bs component of Rb influx. Taken together, these results indicate that the Na + ‐ + ‐ − cotransport activity is critically dependent on cell growth con ditions. © 1993 Wiley‐Liss, Inc.