Effects of procaine on intracellular pH and its regulation: measurements with pH-selective micro-electrodes in Retzius neurones of the leech

The experiments were performed with double-barelled micro-electrodes in Retzius neurones of the leech in order to see if the tertiary amine local anesthetic procaine affects intracellular pH (pH_i) and its regulation. Lasting about 20 min, exposures to procaine (3 mM) saline caused an intracellular alkalosis of about 0.2 pH units which gradually degradated; its removal initiated a fast decrease of pH_i resulting in an acidosis, from which the cells recovered. Detailed studies, involving CO₂ or NH ₄ ⁺ acid loaded cells as well as inhibition of the pH_i regulating exchange mechanism by various drugs or exposures to Na-free salines suggest, that neither the Na⁺–H⁺, nor a probably Na⁺-dependent HCO ₃ ^– –Cl^– exchange are affected by procaine. We propose a model for procaine action on pH_i assuming that neutral procaine passes the membrane easily through lipophilic pathways. The degradation of alkalinity during procaine exposure hints on an entry of loaded procaine, some possible transport paths of which are discussed.