Regulation of cytosolic pH in bovine parathyroid cells: effect of fluoride.
In the present investigation, sodium fluoride (NaF) was employed to explore the role of guanine nucleotide-binding proteins (G-proteins), protein kinase-C, or cytosolic calcium [( Ca]i) in the regulation of cytosolic pH [( pH]i) in dispersed bovine parathyroid cells, using the pH-sensitive fluorescent dye BCECF. When cells acidified by nigericin in Na-free medium were resuspended in Na-containing buffer, [pH]i returned to basal levels. This recovery was blocked by continued removal of Na+ or the addition of amiloride. NaF (10 mM) increased [32P]phosphate incorporation into phosphatidylinositol bisphosphate, suggesting an increase in phosphatidylinositol bisphosphate turnover. NaF caused an initial acidification, followed by an alkaline recovery in a dose-dependent manner (1-10 mM). Amiloride blocked the NaF-induced alkaline recovery. The protein kinase-C activator phorbol 12-myristate 13-acetate (10(-7) M) caused cytosolic alkalinization, while the protein kinase-C inhibitor H7 (6 x 10(-5) M) significantly inhibited the NaF-induced alkaline recovery. Pertussis toxin (1 microgram/ml) did not affect the NaF-induced changes in [pH]i. Removal of extracellular Ca2+ with EGTA blocked the NaF-induced increase in [Ca]i and alkaline recovery. Ionomycin (5 x 10(-7) M) caused cytosolic alkalinization, but pretreatment with EGTA inhibited the ionomycin-induced cytosolic alkalinization. The present studies clearly demonstrated the presence of an amiloride-sensitive Na+/H+ exchanger in parathyroid cells. Our findings suggest that the NaF-induced cytosolic alkaline recovery was via two complementing pathways: 1) activation of protein kinase-C, followed by stimulation of a Na+/H+ exchanger, and 2) existence of extracellular calcium and/or an increase in [Ca]i.
Sugimoto
T
T
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Civitelli
R
R
Ritter
C
C
Slatopolsky
E
E
Morrissey
J
J
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004987:Ethers / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D015759:Ionomycin; D009550:Nigericin / Q000494:pharmacology; D010280:Parathyroid Glands / Q000187:drug effects* / Q000378:metabolism; D037342:Pertussis Toxin; D010710:Phosphates / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology; D012969:Sodium Fluoride / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002352:Carrier Proteins; D004987:Ethers; D010710:Phosphates; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D017923:Sodium-Hydrogen Exchangers; D010566:Virulence Factors, Bordetella; D004533:Egtazic Acid; D015759:Ionomycin; D000584:Amiloride; D012969:Sodium Fluoride; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate; D009550:Nigericin; D002118:Calcium