REGULATION OF INTRACELLULAR PH IN CRYPT CELLS FROM RABBIT DISTAL COLON

H+ secretory mechanisms and intrinsic intracellular buffering capacity were studied in crypt cells from rabbit distal colon. To this end crypts of Lieberkuhn were isolated by microdissection, and intracellular pH (pH(i)) was measured using digital imaging fluorescence microscopy and the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6 )-carboxyfluorescein. In the absence of HCO3--CO2 and presence of Na+, resting pH(i) was 7.51 +/- 0.04 (n = 237/23, cells/crypts). However, 6 min after superfusion with a solution containing zero Na+, 1 x 10(5) M Sch-28080 and 5 x 10(-8) M bafilomycin A(1), pH(i) in cells at the bottom of the crypts was significantly reduced, whereas pHi in cells at the top of the crypts remained unchanged. The intrinsic buffering capacity of cells from the middle to the top portion of crypts was significantly higher in the pH(i) range 7.2-7.6 than of cells at the bottom of the crypt. H+ secretion after an NH4+-NH3 pulse amounted to 245 +/- 53 mu M/s (n = 73/7) at pH(i) 7.1 and was largely Na+ dependent and ethylisopropylamiloride sensitive. The Na+-independent recovery of pH(i) after an acid load was insensitive to Sch-28080 and bafilomycin A(1). In conclusion, pH(i) in colonic crypt cells is regulated through Na+/H+ the crypt axis, whereas Na+/H+ exchange activity and pH(i) did not.