Intracellular pH in rat isolated superior cervical ganglia in relation to nicotine‐depolarization and nicotine‐uptake

Abstract

The intracellular pH (pHi) of rat isolated superior cervical ganglia incubated in normal Krebs solution (pHo = 7·37) was estimated to be 7·33 from the uptake of a weak acid, 14C‐5,5‐dimethyloxazolidine‐2,4‐dione (DMO). Addition of 30 μm nicotine for 30 min reduced the DMO‐estimated pHi by 015 units to 7·18. This effect was prevented by hexamethonium (2·5 mm) or by depolarizing the ganglion with K+ (124 mm). 3H‐Nicotine (30 μm) was concentrated within the ganglia to an intracellular/extracellular concentration ratio (Ci/Co) of 5·54 in normal Krebs solution and 4·61 in 2·5 mm hexamethonium. This would suggest an intracellular pH of 6·54 and 6·63 respectively. In ganglia previously depolarized by K+ the corresponding values for Ci/Co were 402 (minus hexamethonium, estimated pHi 6·95) and 4·17 (plus hexamethonium, estimated pHi 6·94). A multicompartment cell interior comprising an acid cytoplasm (pH˜6·6) and more alkaline nucleus and mitochondria is proposed to explain the difference between the values of pHi estimated from the uptake of DMO and nicotine. It is suggested that the fall in pHi during nicotine‐depolarization results from metabolic stimulation following Na+ entry. 1972 British Pharmacological Society