title: Stimulation of bumetanide-sensitive K+ transport in Swiss 3T3 fibroblasts by serum and mitogenic hormones.
abstract: Rapidly growing Swiss 3T3 fibroblasts possess a bumetanide-sensitive K+ transport system that is dependent on both Na+ and Cl- ions; a smaller bumetanide-insensitive component of K+ transport is also present. In cells brought to the quiescent state by 8-11 days of incubation without a medium change, the bumetanide-sensitive rate of transport was reduced by 63%; the bumetanide-insensitive rate did not change. Removal of dialyzed fetal calf serum from the uptake medium resulted in a substantial reduction in bumetanide-sensitive uptake in both rapidly growing cells (33% reduction) and quiescent cells (68% reduction) but had no effect on bumetanide-insensitive uptake. Insulin was almost as effective as dialyzed fetal calf serum in stimulating bumetanide-sensitive uptake; insulin was maximally stimulatory at 2.5 micrograms/ml. The combination of insulin, epidermal growth factor, and arginine-vasopressin was maximally effective in stimulating both bumetanide-sensitive K+ uptake and 3H-thymidine incorporation in quiescent cells; bumetanide, however, did not interfere with the hormonal stimulation of DNA synthesis. Thus, the bumetanide-sensitive K+ transport system is not necessary for such stimulation to occur. Furthermore, concentrations of hormones which stimulated significant levels of DNA synthesis produced no elevation in the intracellular concentration of K+. We conclude that the bumetanide-sensitive pathway of K+ transport is modulated by serum and by mitogenic hormones, but does not play a role in the stimulation of DNA synthesis by these factors.
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D001769:Blood; D002034:Bumetanide / Q000494:pharmacology*; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D004232:Diuretics / Q000494:pharmacology*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005347:Fibroblasts; D007328:Insulin / Q000494:pharmacology*; D007399:Interphase; D051379:Mice; D011188:Potassium / Q000378:metabolism*
chemical_list: D004232:Diuretics; D007328:Insulin; D002034:Bumetanide; D001127:Arginine Vasopressin; D004815:Epidermal Growth Factor; D004247:DNA; D011188:Potassium