[Intracellular pH regulation in human SW-620 colon cancer cells]

Intracellular pH (pHi) regulation is essential for basic functioning of the cell and activation of pHi regulatory mechanisms appears to be involved in the initial stage of cell division. Little is known about pHi regulation in human colonic carcinoma cells. We investigated SW-620 (CCL 227) cells, a cell-line derived from a human colonic adenocarcinoma. pHi changes were recorded by computer-assisted spectrofluorimetric monitoring of the pH-sensitive, fluorescent dye BCECF (2',7'-bis(carboxyethyl)- 5(6)carboxyfluorescein). Resting pHi in HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) buffered solution was 7.53 +/- 0.01. Intracellular acidification after an ammonium prepulse produced a pHi decline of 0.5 units and pHi returned to normal value in NaCl Ringer's. Both 1 mM amiloride and Na-free solution completely inhibited recovery for 8 minutes. This inhibition was reversible in NaCl Ringer's. Na-free solution led to a pHi decrease to 7.39 +/- 0.04 after 16 min, pHi was also lowered by 8 minute incubation of cells with 1 mM amiloride (7.40 +/- 0.02). In HCO3/CO2-buffered solution resting pHi was 7.42 +/- 0.01 (n = 35). Recovery from an acute acid load, induced by NH4 prepulse or switching from HEPES- to bicarbonate-buffered solution, was Na dependent, Cl independent, reversible and only partially blocked by 1 mM amiloride - pHi slowly recovered from 6.83 +/- 0.03 to 7.00 +/- 0.06 in 8 minutes. In the presence of amiloride and 200 microns H2DIDS (dihydro-4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) pHi recovery was completely inhibited for 8 minutes. In Na-free solution pHi decreased from 7.44 +/- 0.04 to 7.29 +/- 0.03 within 8 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)