Growth regulation of LLC-PK1 cells: lack of effect of Na(+)-loading.
To gain more information about the growth regulation of renal epithelial cells, we examined the growth stimulatory effect of serum and intracellular sodium in the renal epithelial cell line, LLC-PK1. In subconfluent LLC-PK1 cells serum-starved for 5 days and exposed to [3H]thymidine for 24 h, 22.9% of the cells synthesized DNA. Stimulation with 10% foetal calf serum (FCS) caused an almost three-fold increase in the fraction of labelled nuclei (62.2%). Serum-starved LLC-PK1 cells exposed to 10% FCS responded with an increased abundance of c-jun transcripts. The maximal expression of the c-jun transcripts occurred at 60 min and declined 120 min after serum stimulation. It has been suggested that an increase in Na+ influx plays a role in the growth regulation of renal epithelial cells. This prompted us to study the effect of intracellular Na+ loading on the growth response of LLC-PK1 cells. Serum-starved LLC-PK1 cells were incubated in a low K+ medium or exposed to Nystatin. Incubation in a low K+ medium or with Nystatin resulted in a marked increase in intracellular Na after only 5 min. A low K+ medium did not significantly influence the intracellular pH. No effect was observed on DNA synthesis or the abundance of c-jun transcripts in LLC-PK1 cells. Nor did Na+ loading enhance the growth stimulatory effect of serum. The results suggest that an increase in intracellular sodium does not directly regulate the growth of renal epithelial cells.
Ostlund
E
E
Department of Pediatrics, St. Göran's Children's Hospital, Stockholm, Sweden.
Larsson
S H
SH
Wroblewski
R
R
Wroblewski
J
J
Aperia
A
A
D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004577:Electron Probe Microanalysis; D004847:Epithelial Cells; D004848:Epithelium / Q000737:chemistry / Q000502:physiology; D015870:Gene Expression / Q000235:genetics; D016758:Genes, jun / Q000235:genetics; D007672:Kidney Cortex / Q000737:chemistry* / Q000166:cytology* / Q000502:physiology; D009761:Nystatin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000032:analysis* / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000502:physiology; D013552:Swine; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D014316:Tritium
D016895:Culture Media, Serum-Free; D014316:Tritium; D009761:Nystatin; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D013936:Thymidine