INTERACTIONS BETWEEN INTRACELLULAR pH AND CALCIUM IN‐SINGLE MOUSE NEUROBLASTOMA (N2A) AND RAT PHEOCHROMOCYTOMA CELLS (PC12)

Abstract

Intracellular pH (pHi) was measured at the tips of extending neurites and in the corresponding cell bodies of single cultured mouse neuroblastoma (N2A) and rat pheochromocytoma cells (PC12) using the fluorescent dye 2,3‐di‐cyanohydroquinone (DCH). It was observed that pHi at the tip of an extending neurite was consistently 0·2‐0·3 pH units higher than pHi in the cell body. Experiments performed on whole cells to establish the types of cellular mechanism which could be responsible for such regional differences demonstrate the presence of Na+‐H+ exchange and Cl−‐HCO3− exchange in these cells. Since regional variations in Cai2+ have been reported between neurites and the cell body, experiments were performed to examine the possible interactions between pHi and Cai2+. Intracellular calcium was measured using the fluorescent Ca2+‐sensitive dye Indo‐1. An increase in pHi, on application of NH4Cl, resulted in a transient elevation of Cai2+. On subsequent acidification, on removal of NH4Cl, there was a further transient increase in Cai2+. These changes in Cai2+ were also present in solutions with low calcium suggesting that Cai2+ is mobilized from within the cell. The results are discussed in terms of possible mechanisms whereby the extension and retraction of cell processes could be influenced by Cai2+ and modulated by pHi. © 1989 The Physiological Society