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Changes in intracellular pH and pH regulating mechanisms in somitic cells of the early chick embryo: a study using fluorescent pH‐sensitive dye.
Author(s) -
Gillespie J I,
Greenwell J R
Publication year - 1988
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1988.sp017338
Subject(s) - dids , amiloride , intracellular ph , chemistry , intracellular , biophysics , fluorescence , sodium , biochemistry , biology , membrane , physics , quantum mechanics , organic chemistry
1. Measurements of intracellular pH (pHi) have been made using the fluorescent dye dicyano‐hydroquinone (DCH) in somites isolated from 2‐day‐old chick embryos. Measurements of pHi, from freshly dissected somites, gave values of 7.18 +/‐ 0.02 (mean +/‐ S.D., n = 12) while in somites kept in media containing 10% fetal calf serum for 2‐5 h pHi was 7.36 +/‐ 0.02 (n = 11). 2. In freshly dissected control tissue recovery from an acid load (NH4Cl pre‐pulse), in the nominal absence of HCO3‐, was 0.007 +/‐ 0.003 pH units/min (n = 11). In the presence of 5 mM‐HCO3‐ the rate of recovery was increased to 0.132 +/‐ 0.003 pH units/min (n = 11). This HCO3(‐)‐dependent recovery was inhibited by pre‐treatment with DIDS (5 X 10(‐4) M) and stopped when Na+ was replaced in the bathing medium with K+ or N‐methylglucamine. Amiloride (10(‐3) M) had no effect. 3. Replacement of Cl‐ with gluconate had little effect on pHi in control somites suggesting that absence of Cl(‐)‐HCO3‐ exchange. 4. These observations are consistent with the presence of a coupled Na+‐HCO3‐ entry and the absence of Na+‐H+ exchange. 5. In serum‐treated cells recovery from an acid load was 0.101 +/‐ 0.01 pH units/min (n = 11) in the nominal absence of HCO3‐. Increasing the HCO3‐ concentration (5‐10 mM) or pre‐treatment with DIDS had no effect on the rate of acid extrusion. Recovery is Na+ dependent and inhibitable with amiloride, indicating the presence of Na+‐H+ exchange. 6. These results suggest that during somitic development the mechanisms regulating pHi and recovery from acid loading are modified from a Na+‐HCO3‐ influx to a Na+‐H+ exchanger. This transition allows the cells to increase pHi by up to 0.2 pH units and may have a role in somitic cell development.