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Regulation of Na + /H + and Cl − /HCO 3 − antiports in vero cells
Author(s) -
Tønnessen Tor Inge,
Aas Alf Tore,
Ludt Jannikke,
Blomhoff Heidi Kiil,
Olsnes Sjur
Publication year - 1990
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041430125
Subject(s) - antiporter , incubation , chemistry , forskolin , vero cell , intracellular , ion transporter , intracellular ph , sodium–hydrogen antiporter , n ethylmaleimide , sodium , nuclear chemistry , biochemistry , microbiology and biotechnology , medicinal chemistry , biology , membrane , in vitro , organic chemistry
Abstract The effect of serum, phorbol‐12‐myristate‐13‐acetate (TPA), and forskolin on the activity Na + /H + antiport and the Na + ‐coupled and Na + ‐independent Cl − / HCO 3 − antiport was studied in Vero cells by measuring 22 Na + and 36 Cl − fluxes and changes in cytosolic pH (pH i ). The Na + ‐independent Cl − /HCO 3 − antiport, which acts as an acidifying mechanism, is strongly pH‐sensitive. In serum‐starved cells it is activated at alkaline cytosolic pH, with a half‐maximal activity at pH i ∼7.20. Incubation with serum increased the activity of the Na + ‐independent Cl − /HCO 3 − antiport at pH i values from 6.8 to 7.2. Thus serum appeared to alter the pH i sensitivity of this antiporter such that the threshold value for activation of the antiport was shifted to a more acidic value. Na + /H + antiport was somewhat stimulated initially by addition of serum, but further incubation with serum (> 45 min) decreased its activity. The activity of the Na + ‐coupled Cl − /HCO 3 − antiport, which is the major alkalinizing antiport in Vero cells, was not altered by short‐term incubation with serum (< 10 min) but decreased after prolonged incubation (> 45 min). Our findings with TPA and forskolin indicate that the effect of serum is partly mediated by the protein kinase C pathway, whereas the cyclic adenosine monophosphate pathway does not appear to play an important role. The net effect of serum on the pH i ‐regulating antiports was a slight decrease in intracellular pH.