Release of non-neuronal acetylcholine from the human placenta: difference to neuronal acetylcholine

Abstract

The synthesis and release of non-neuronal acetylcholine, a widely expressed signaling molecule, were investigated in the human placenta. This tissue is free of cholinergic neurons, i.e. a contamination of neuronal acetylcholine can be excluded. The villus showed a choline acetyltransferase (ChAT) activity of 0.65 nmol/mg protein per h and contained 500 nmol acetylcholine/g dry weight. In the absence of cholinesterase inhibitors the release of acetylcholine from isolated villus pieces amounted to 1.3 nmol/g wet weight per 10 min corresponding to a fractional release rate of 0.13% per min. The following substances did not significantly modify the release of acetylcholine: oxotremorine (1 microM), scopolamine (1 microM), (+)-tubocurarine (30 microM), forskolin (30 microM), ouabain (10 microM), 4alpha-phorbol 12,13-didecanoate (1 microM) and tetrodotoxin (1 microM). Removal of extracellular calcium, phorbol 12,13-dibutyrate (1 microM) and colchicine (100 microM) reduced the acetylcholine release between 30% and 50%. High potassium chloride (54 mM and 108 mM) increased the acetylcholine release slightly (by about 30%). A concentration of 10 microM nicotine was ineffective, but 100 microM nicotine enhanced acetylcholine release gradually over a 50-min period without desensitization of the response. The facilitatory effect of nicotine was prevented by 30 microM (+)-tubocurarine. Inhibitors of cholinesterase (physostigmine, neostigmine; 3 microM) facilitated the efflux of acetylcholine about sixfold, and a combination of both (+)-tubocurarine (30 microM) and scopolamine (1 microM) halved the enhancing effect. In conclusion, release mechanisms differ between non-neuronal and neuronal acetylcholine. Facilitatory nicotine receptors are present which are activated by applied nicotine or by blocking cholinesterase. Thus, cholinesterase inhibitors increase assayed acetylcholine by two mechanisms, protection of hydrolysis and stimulation of facilitatory nicotine receptors.

M3 Muscarinic Receptor Antagonists Inhibit Small Cell Lung Carcinoma Growth and Mitogen-Activated Protein Kinase Phosphorylation Induced by Acetylcholine Secretion

“…Five of six SCLC cell lines examined here synthesized and secreted acetylcholine. This is consistent with the reports that acetylcholine is synthesized and secreted by nonneuronal cell types, including airway epithelial cells (7,36), vessel endothelial cells (37), lymphocytes (38), ovarian granulosa cells (39), and placenta (40). During a 24-h incubation, >100 pmol of acetylcholine were secreted by 5 Â 10 5 H82 cells, and the acetylcholine concentration in the medium reached 150 nmol/L, a concentration sufficient to trigger [Ca 2+ ] I increase in SCLC cells (Fig.…”

Expression of the cholinergic gene locus in the rat placenta

“…Human and rat placenta are rich in ChAT and ACh (Loewi and Navratil 1926;Sastry et al 1976;Stevens et al 1976;Stabile et al 1989;King et al 1991;Wessler et al 2001a). The multiple functions of ACh in placenta include: (1) modification of uterine functions during pregnancy and labour (Sastry 1997) and (2) control of amino acid transport between maternal and fetal sides (Bull et al 1961;Rowell and Sastry 1978).…”

Complex bifurcation/chaotic behavior of acetylcholinesterase and cholineacetyltransferase enzymes system

“…Because of the lack of good experimental data on human brain, our research is limited by the use of properly chosen dimensionless parameters in order to investigate the main characteristics of this coupled enzyme system (the values are taken from measurements on rat and guinea pig brain as well as from some available data on humans [5,[34][35][36][37][38]). …”

“…While, in guinea pig cerebral cortex the range was 0.31 · 10 À5 (free ACh) to 1.67 · 10 À5 (total ACh) [38]. • ACh concentration in human placenta is reported to be in the range of 3.0 · 10 À5 to 55.5 · 10 À5 [36]. • ACh in the isolated rings of rat pulmonary artery was measured to be in the range of 0.001 · 10 À5 to 3.0 · 10 À5 [37].…”