C. James Kirkpatrick1,*, Fernando Bittinger1, Ron
E. Unger1, Jšrg Kriegsmann1, Heinz Kilbinger2
and Ignaz Wessler2
1Institute of Pathology and 2Institute of Pharmacology,
Johannes Gutenberg University, Langenbeckstr. 1, D-55101 Mainz, Germany
*Corresponding author. FAX: +49-6131-17-6695
E-mail: kirkpatrick@pathologie.klinik.uni-mainz.de
Abstract: An increasing body of knowledge indicates that the cholinergic
system is not confined to the nervous system, but is practically ubiquitous.
The present paper will address the question of the non-neuronal cholinergic
system in vascular endothelial cells (EC). In tissue sections of human skin,
immunohistochemical studies using confocal laser scanning microscopy showed
ChAT (choline acetyltransferase) activity in the EC of dermal blood vessels.
Positive ChAT immunoreactivity was also demonstrated in monolayer cultures
of human umbilical vein EC (HUVEC) and a human angiosarcoma EC line (HAEND).
That the synthesizing enzyme is not only present in EC, but also active
was shown by measuring ChAT activity. Thus, in HUVEC cultures, ChAT activity
amounted to 0.78±0.15 nmol á mg protein-1
á h-1 (n = 3), but was only partially
(about 50%) inhibited by the ChAT inhibitor bromoacetylcholine (30 mM).
In HPLC measurements, a concentration of 22±2 pmol acetylcholine (ACh) per
106 cells was found (n = 6). However, using a cholinesterase-packed
analytical column to check the identity of the acetylcholine peak, the peak
height was found to be reduced, although a significant peak still remained,
indicating the existence of a compound closely related to ACh. Further immunocytochemical
experiments indicated that EC in vitro also express the vesicular acetylcholine
transporter (VAChT) system. Preliminary immunoelectron microscopic studies
suggest a topographical association of VAChT with endothelial endocytotic
vesicles. The presented experiments clearly demonstrate the existence of
essential elements of the cholinergic system (ChAT, VAChT, ACh) in the human
endothelium. The biological functions of ACh synthesized by endothelial
cells are the focus of ongoing research activity.
Keywords: Non-neuronal cholinergic system, Endothelium, Signal transduction
Copyright The Japanese Pharmacological Society
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