Identification of a sodium-bicarbonate symport in human platelets.

Abstract

Intracellular pH (pH(i)) was measured in human platelets using fluorescent probes. Basal pH(i) was higher in HC(O3-)- buffered solutions (7(7.33 +/- 0.01) than in nominally HCO3- free, Hepes buffered solutions (7.16 +/- 0.01, P < 0.05). Addition of EIPA caused to fall in Hepes, but did not inhibit the increase of pH(i) when platelets maintained in Hepes were transferred to a CO2/HCO3- buffer. After an intracellular acidosis induced by an NH4Cl prepulse, the initial velocity of recovery (d(pH)/dt(i), in pH units/min) was 3.32 +/- 0.69 in Hepes-buffered solution and 2.85 +/- 0.88 in HCO3- media. Taking into account the differences in buffer capacity, the efflux of acid equivalents after 1.2 min was twice as much in the presence of bicarbonate. The addition of 30 mumol/1 EIPA effectively blocked acid efflux (d(pH)/dt(i) = 0.08 +/ 0.04) in a nominally HCO3- free solution, whereas the recovery was reduced but not abolished (d(pH)/dt(i) = 0.37 +/- 0.10, P < 0.05) in the presence of bicarbonate. The stilbene derivative SITS further inhibited the EIPA-resistant pH(i) recovery. Removal of external Na+ inhibited the HCO(3-)-dependent recovery whereas depletion of internal Cl-, did not suppress it. Depolarization of the membrane had no effect on this recovery. The results suggest the contribution of an electroneutral Na+/HCO3- cotransport in the recovery of pH(i) following an acid load. Both the Na+/H+ antiport and the HCO(3-)-dependent mechanism contribute approx. 50% each to the total acid equivalent efflux during the recovery from a pH(i) 6.46 +/- 0.14 to the basal pH(i) in human platelets.

• Authors: O A Gende, H E Cingolani
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1278 Issue 1 Pg. 119-24 (Jan 12 1996) ISSN: 0006-3002 [Print] Netherlands
• PMID: 8611598 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Bicarbonates
• Carrier Proteins
• Chlorides
• Sodium-Bicarbonate Symporters
• 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid
• Amiloride
• Sodium
• Potassium
• ethylisopropylamiloride

Topics

• 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid (pharmacology)
• Amiloride (analogs & derivatives, pharmacology)
• Bicarbonates (blood)
• Biological Transport (drug effects)
• Blood Platelets (metabolism)
• Carrier Proteins (blood)
• Chlorides (pharmacology)
• Humans
• Hydrogen-Ion Concentration
• Potassium (pharmacology)
• Sodium (blood)
• Sodium-Bicarbonate Symporters