THE REGULATION OF INTRACELLULAR PH IN MONKEY KIDNEY EPITHELIAL-CELLS (BSC-1) - ROLES OF NA+/H+ ANTIPORT, NA+-HCO3--(NACO3-) SYMPORT, AND CL-/HCO3- EXCHANGE

  • 15 September 1986
    • journal article
    • research article
    • Vol. 261  (26) , 2120-2127
Abstract
Using the pH-sensitive absorbance of 5 (and 6)-carboxy-4'',5-dimethylfluorescein, we investigated the regulation of cytoplasmic pH (pHi) in monkey kidney epithelial cells (BSC-1). In the absence of .**GRAPHIC**. pHi is 7.15 .+-. 0.1, which is not significantly different from pHi in 28 mM .**GRAPHIC**. 5% CO2 (7.21 .+-. 0.07). After an acid load, the cells regulate pHi in the absence of .**GRAPHIC**. by a Na+ (or Li+)-dependent, amiloride-inhibitable mechanism (indicative of Na+/H+ antiport). In 28 mM .**GRAPHIC**. while still dependent on Na+, this regulation is only blocked in part by 1 mM amiloride. A partial block is also observed with 4,4''-diisothiocyanostilbene-2,2''-disulfonic acid (DIDS) (1 mM). With cells pretreated with DIDS, 1 mM amiloride nearly totally inhibits this regulation. Cl- had no effect on pHi regulation in the acidic range. In .**GRAPHIC**. saline, Na+ removal leads to an amiloride-insensitive acidification, which is dependent on Ca2+. In 28 mM .**GRAPHIC**. Na+ (and Ca2+) removal led to a pronounced reversible and DIDS-sensitive acidification. When .**GRAPHIC**. was lowered from 46 to 10 mM at constant pCO2 (5%), pHi dropped by a DIDS-sensitive mechanism. Identical changes in pHo (7.6 to 6.9) in the nominal absence of .**GRAPHIC**. to smaller changes of pHi. In the presence but not in the absence of .**GRAPHIC**. removal of Cl- led to a DIDS-sensitive alkalinization. This was also observed in the nominal absence of Na+, which leads to a sustained acidification. It is concluded that in nominally bicarbonate-free saline, the amiloride-sensitive Na+/H+ antiport is the predominant mechanism of pHi regulation at acidic pHi, while being relatively inactive at physiological values of pHi. In bicarbonate saline, two other mechanisms affect pHi regulation: a DIDS-sensitive Na+ .**GRAPHIC**. symport, which contributes to cytoplasmic alkalinization, and a DIDS-sensitive .**GRAPHIC**. exchange, which is apparently independent of Na+.