Acetylcholine and choline in rat adrenals and brain cortex prisms incubated at elevated concentrations of choline in...

Experiments were performed with rat adrenals and brain cortex prisms incubated in vitro in order to clarify whether it is possible to increase their acetylcholine (ACh) content by adding a high concentration of choline to the medium and whether the additional ACh formed can be released by subsequent depolarization. After 60 min incubation with 0.5 mmol/l choline, the concentration of ACh in the adrenals was increased by 116% (compared to the incubation without added choline), while in cortical prisms the observed increase (by 37%) was statistically non-significant. The content of ACh in both tissues was raised by paraoxon during incubations without added choline, but paraoxon did not augment the increased concentration of ACh in tissues incubated with added 0.5 mmol/l choline. The ACh that accumulated in the adrenals during 60 min preincubations with added choline could be released during subsequent depolarizing incubations; the release was Ca2+ independent. In contrast to brain cortex prisms and to the adrenals preincubated without choline, no resynthesis of ACh occurred during the period of depolarization in the adrenals preincubated with 0.5 mmol/l choline. Large amounts of choline accumulated in both tissues during incubations with 0.5 mmol/l choline and the accumulated choline could be released by depolarization; the release of choline from the adrenals was Ca2+ independent. Free choline was produced in the adrenals (presumably from choline esters) during the periods of depolarization. The reason for differences between the effects of increased concentrations of choline on ACh in the adrenals and in brain cortex is not known.(ABSTRACT TRUNCATED AT 250 WORDS)