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Characterization of Na+-K+ homeostasis of cultured human skin fibroblasts in the presence and absence of fetal bovine serum

✍ Scribed by Laszlo Hopp; Norman Lasker; Ronie Bamforth; Abraham Aviv

Publisher
John Wiley and Sons
Year
1992
Tongue
English
Weight
619 KB
Volume
151
Category
Article
ISSN
0021-9541

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✦ Synopsis

New lersey 07 I03

Previously, we demonstrated that removal of fetal bovine serum (FBS) from the medium of human skin fibroblasts resulted in an accelerated '%b' washout, decreased cellular K i , 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 Kt were measured. Verapamil (K,,, = 15 pM) and chlorpromazine (K,,, = 1 pM) reduced by approximately 70% the increased '6Rb+ 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 KM) was only partially effective in offsetting the enhanced '"Rb' 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 '"Rb' washout. The protein kinase C activator phorbol 12-myristate 13-acetate enhanced the '"Rb' 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 t contents were not changed by the phorbol ester. We conclude that FBS removal raises the cellular Na+ content, and enhances "Rb+ efflux, through a calmodulin-dependent pathway activated by calcium influx.

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