title: Characterization of Na(+)-K+ homeostasis of cultured human skin fibroblasts in the presence and absence of fetal bovine serum.
abstract: Previously, we demonstrated that removal of fetal bovine serum (FBS) from the medium of human skin fibroblasts resulted in an accelerated 86Rb+ washout, decreased cellular K+, and increased Na+ contents. In the present study we examined the mechanism underlying these changes. The efflux rate constant for 86Rb+, and the cellular contents of Na+ and K+ were measured. Verapamil (K1/2 = 15 microM) and chlorpromazine (K1/2 = 1 microM) reduced by approximately 70% the increased 86Rb+ washout evoked by FBS removal. The effect of the two drugs was additive at low, but not high, concentrations. Verapamil and chlorpromazine also attenuated the decrease in cellular K+ content and prevented the increase in cellular Na+ content associated with FBS depletion. Bumetanide (50 microM) was only partially effective in offsetting the enhanced 86Rb+ efflux and was completely without any effect on the cellular Na+ and K+ changes induced by FBS removal. In the presence of FBS, A-23187 produced a slight and transient increase of the 86Rb+ washout. The protein kinase C activator phorbol 12-myristate 13-acetate enhanced the 86Rb+ efflux in FBS-containing medium for a prolonged period but this increase was only a fraction of that caused by serum removal. Cellular Na+ and K+ contents were not changed by the phorbol ester. We conclude that FBS removal raises the cellular Na+ content, and enhances 86Rb+ efflux, through a calmodulin-dependent pathway activated by calcium influx.
authors.affiliation: Hypertension Research Center, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark 07103.
authors.forename: L
authors.initials: L
authors.lastname: Hopp
authors.forename: N
authors.initials: N
authors.lastname: Lasker
authors.forename: R
authors.initials: R
authors.lastname: Bamforth
authors.forename: A
authors.initials: A
authors.lastname: Aviv
mesh_terms: D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D003470:Culture Media; D005333:Fetus; D005347:Fibroblasts / Q000378:metabolism*; D006706:Homeostasis; D007425:Intracellular Membranes / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology; D012413:Rubidium / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000502:physiology*; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D003470:Culture Media; D002034:Bumetanide; D012710:Serum Albumin, Bovine; D012964:Sodium; D011493:Protein Kinase C; D012413:Rubidium; D011188:Potassium; D002118:Calcium