title: Lowering extracellular Na+ concentration releases autocrine growth factors from renal epithelial cells.
abstract: Sodium influx is an important early signal during the onset of mitogenesis in many types of cells. From this observation, one would predict that a decrease in extracellular Na+ concentration might retard cell proliferation. We tested this prediction by exposing sets of cultures of monkey kidney epithelial cells (BSC-1 line) to medium with progressively reduced concentrations of Na+, and we measured the effect on cell multiplication. Unexpectedly, a reduction of the Na+ concentration from 155 mM (control) to 130 mM stimulated proliferation of epithelial cells but not of fibroblasts. Exposure of BSC-1 cells to low Na+ medium for 5 min was sufficient to commit them to accelerated growth. Further study revealed that the cells released two growth factors during this period: anionic proteins with apparent molecular weights of 6200 and 9000 whose properties differ from those of other known growth factors. Thus, a reduction in extracellular Na+ concentration apparently signaled the rapid release of autocrine growth factors that stimulate renal epithelial cell multiplication.
authors.forename: M M
authors.initials: MM
authors.lastname: Walsh-Reitz
authors.forename: S L
authors.initials: SL
authors.lastname: Gluck
authors.forename: S
authors.initials: S
authors.lastname: Waack
authors.forename: F G
authors.initials: FG
authors.lastname: Toback
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004848:Epithelium / Q000502:physiology; D005110:Extracellular Space / Q000502:physiology; D006133:Growth Substances / Q000302:isolation & purification / Q000502:physiology*; D007668:Kidney / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008970:Molecular Weight; D012964:Sodium / Q000502:physiology*
chemical_list: D006133:Growth Substances; D012964:Sodium