naphthylvinylpyridine and (2-benzoylethyl)trimethylammonium

The synthesis and release of acetylcholine (ACh) was studied in term human placental villous mince in vitro. During a 140-min incubation the placental tissue synthesized ACh at a rate of 2.59 nmol/g/min and released ACh into the medium at a rate of 0.78 nmol/g/min. Consequently there was an increase in tissue levels of ACh from an initial value of 83 to 321 nmol/g. Inhibition of choline acetyltransferase by 2-benzoylethyl trimethylammonium or 4-(1-naphthylvinyl)pyridine depressed the synthesis of ACh by over 75% and blocked the increase in tissue levels of ACh. The IC50 values for the inhibition of ACh synthesis and decrease in tissue levels were close to the IC50 values determined for inhibition of choline acetyltransferase in situ. Neither 2-benzoylethyl trimethylammonium nor 4-(1-naphthylvinyl)pyridine caused a significant effect on ACh release. 2-benzoylethyl trimethylammonium and 4-(1-naphthylvinyl)pyridine were quite effective in inhibiting the uptake of the neutral amino acid, alpha-aminoisobutyric acid, into the tissue. The inhibition of alpha-aminoisobutyric acid uptake paralleled the inhibition of ACh synthesis. These results support the hypothesis of an association between placental cholinergic activity and amino acid transport in the human placenta.

Topics: Acetylcholine; Aminoisobutyric Acids; Biological Transport; Choline; Choline O-Acetyltransferase; Female; Humans; In Vitro Techniques; Naphthylvinylpyridine; Placenta; Pregnancy

(2-Benzoylethyl)trimethylammonium chloride (BETA), bromoacetylcholine and 4-(1-naphthylvinyl)pyridine are potent inhibitors of choline acetyltransferase (ChA). In order to evaluate the role of acetylcholine in human placenta, the effects of the above ChA inhibitors on the uptake of [alpha-14C]aminoisobutyric acid (AIB) by isolated human placental villi were studied. All three inhibitors were able to inhibit AIB uptake by the tissue. The ID50 for BETA, the most potent compound, was about 6.2 x 10(-5) M. The blockade of AIB uptake closely paralleled the potency for inhibition of ChA in a series of keto-analogs of acetylcholine related to BETA. There was a positive relationship between the blockade of AIB uptake and the inhibition of ChA by BETA in situ. Hemicholinium-3 had no significant effect on AIB uptake. The ChA inhibitors did not exhibit significant effects on cell viability as determined by tissue lactic dehydrogenase. These observations indicate that the uptake of neutral amino acids by human placental villus is linked to acetylcholine synthesis.

Topics: Acetylcholine; Aminoisobutyric Acids; Biological Transport; Cell Survival; Choline O-Acetyltransferase; Chorionic Villi; Culture Techniques; Dose-Response Relationship, Drug; Female; Humans; Kinetics; Naphthylvinylpyridine; Placenta; Pregnancy