PT  - JOURNAL ARTICLE
AU  - George B. Weiss
TI  - DEPENDENCE OF NICOTINE-C<sup>14</sup> DISTRIBUTION AND MOVEMENTS UPON pH IN FROG SARTORIUS MUSCLE
DP  - 1968 Mar 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 135--147
VI  - 160
IP  - 1
4099  - http://jpet.aspetjournals.org/content/160/1/135.short
4100  - http://jpet.aspetjournals.org/content/160/1/135.full
SO  - J Pharmacol Exp Ther1968 Mar 01; 160
AB  - The uptake and efflux of methyl-C14-labeled nicotine in frog sartorius muscle are measured at pH 8.40 and pH 7.40. At both pH levels nicotine-C14 uptake is about 90% of maximum in 10 min. The total tissue space occupied after 1-hr incubation is 2.722 ± 0.155 times the extracellular concentration of nicotine at pH 8.40 and 1.003 ± 0.089 times at pH 7.40. Lowering the extracellular pH initiates a sustained increase in the efflux rate of nicotine-C14, whereas raising the pH decreases efflux. Addition of 2.50 mM nonradioactive nicotine induces a transient increase in the rate of loss of nicotine-C14 which is larger at pH 8.40 than at pH 7.40. Nornicotine (10.0 mM) initiates a similar but much smaller transient increase in nicotine-C14 efflux and also a sustained increased efflux, whereas cotinine, a nicotine metabolite, has no effect on nicotine-C14 uptake or efflux. Intracellular pH estimations derived from C14-labeled 5,5-dimethyl-2,4-oxazolidinedione tissue spaces indicate that nicotine is distributed across the cell membrane in accordance with the pH gradient. The transient increase in nicotine release may represent a displacement of bound nicotine from sites in the cell membrane, whereas alterations in extracellular pH are rapidly followed by shifts in intracellular nicotine-C14 that appear to be due to an altered backflux of nicotine-C14 into the muscle cell. © 1968 by The Williams & Wilkins Company