J L Rodeau — Page 2 | Search PubMed

PubMedDate not supplied

Intracellular pH regulation in ventral horn neurones cultured from embryonic rat spinal cord.

Intracellular pH was measured with the pH-sensitive fluorescent probe BCECF in spinal cord neurones cultured from rat embryos. At an external pH of 7.3, the average steady-state pHi was 7.18 +/- 0.03 (SEM, n = 97) and 7.02 +/- 0.01 (n = 221) in HEPES-buffered and in bicarbonate-buffered medium, respectively. In both external media, pHi was strongly dependent on external pH (pHe). In HEPES-buffered medium, pHi recovery following an acid load induced by transient application of ammonium required external Na+ and was inhibited by amiloride, indicating the presence of a Na+/H+ exchange. Na(+)- and HCO3(-)-dependent, DIDS-sensitive alkalinizing mechanisms also contributed to pHi regulation in CO2/bicarbonate-buffered medium. The presence of an electrogenic Na(+)-HCO3- cotransporter was confirmed by the alkalinizing effect of KCl application. The fact that pHi is lower in CO2/bicarbonate- than in HEPES-buffered medium and the alkalinization observed upon suppression of external Cl- suggest that the acidifying Cl-/HCO3- transporter plays an important role in defining pHi.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMedDate not supplied

Effect of procaine on membrane potential and intracellular pH in Xenopus laevis oocytes.

The effect of the local anaesthetic procaine on the intracellular pH, pHi, and electrophysiological properties of full-grown Xenopus oocytes was studied. In spite of its interference with both the pH-sensitive microelectrodes and fluorescent probe BCECF, we have shown that procaine induced an intracellular acidification rather than the alkalization commonly observed in most cells. The resting pHi of Xenopus oocytes loaded with BCECF was 7.36 +/- 0.04 (n = 16). Addition of 10 mM procaine to the bath at pH 7.5 caused pHi to decrease to a new steady state value of 6.97 +/- 0.05 (n = 9). A similar behaviour of pHi was observed with microelectrodes. Procaine also promoted a rise in membrane conductance and a membrane depolarization. These changes in membrane potential and conductance were not caused by the decrease in pHi since the addition of sodium propionate at pH 7.5 produced the same decrease of pHi as procaine, but resulted in only a slight depolarization with superimposed oscillations. Current measurements using two-electrode voltage clamp showed that the depolarization was associated with an inward current. No significant effect on this current was observed when replacing Cl, K or Na in the external medium. The absence of effect of Cl and K channel inhibitors argues against the involvement of Cl and K currents during the procaine response.

Ammonium Chloride↗