Welsch F, Wenger W C, Stedman D B
Placenta Suppl. 1981;3:339-51.
Choline acetyltransferase (ChAc), the enzyme catalysing the biosynthesis of acetylcholine (ACh) in the non-innervated human placenta, was rapidly and persistently inhibited by (2-benzoylethyl)trimethylammonium (BETA) when the drug was applied to intact tissue fragments. This inhibition (50 per cent at congruent to 0.4 mmol/1 BETA) was coupled to a concomitant reduction in the active uptake against a concentration gradient of the nonmetabolizable amino acid alpha-aminoisobutyric acid (AIB). The reduction of AIB accumulation (50 per cent at congruent to 0.1 mmol/1 BETA) was temporally related to inhibition of ChAc. These effects suggest that AIB uptake by the human placenta and ACh biosynthesis catalysed by ChAc are related. Measurements of total ACh content in tissue samples treated in parallel with those destined for ChAc and AIB uptake determinations revealed that BETA (3 mmol/1) significantly reduced the ACh levels by 35 to 50 per cent. This drug concentration caused almost complete inhibition of ChAc and blockade of AIB accumulation.
胆碱乙酰转移酶（ChAc）是在无神经支配的人胎盘中催化乙酰胆碱（ACh）生物合成的酶，当将药物（2-苯甲酰乙基）三甲基铵（BETA）应用于完整的组织片段时，它会迅速且持续受到抑制。这种抑制作用（在约0.4 mmol/L BETA时达到50%）伴随着不可代谢氨基酸α-氨基异丁酸（AIB）逆浓度梯度的主动摄取的相应减少。AIB积累的减少（在约0.1 mmol/L BETA时达到50%）在时间上与ChAc的抑制相关。这些效应表明人胎盘对AIB的摄取与ChAc催化的ACh生物合成有关。与用于ChAc和AIB摄取测定的组织样品平行处理的组织样品中总ACh含量的测量结果显示，BETA（3 mmol/L）可使ACh水平显著降低35%至50%。该药物浓度几乎完全抑制了ChAc并阻断了AIB的积累。
