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Neuronal traits of an endocrine cell type: Granulosa cells of the ovary
Author(s) -
Mayerhofer Artur,
Kunz Lars
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a353-c
Subject(s) - microbiology and biotechnology , medicine , endocrinology , biology , cholinergic , acetylcholine , vesicular acetylcholine transporter , ovarian follicle , chemistry , follicular phase , choline acetyltransferase
The adult mammalian ovary is a highly dynamic organ, in which proliferation and differentiation processes occur constantly, e.g. during follicular growth. Hormones and neurotransmitters are thought to be involved, however, granulosa cells (GCs) of the follicle, which proliferate and differentiate during follicular growth, are not in direct contact to blood vessels, which deliver hormones and are resticted to the theca region. GCs are likewise separated from nerve fibers, a major source of neurotransmitters. Based on this fact, a role of intrafollicular, oocyte and GC derived, local signalling molecules in orchestration of follicular growth is being more and more recognized. To gain insights into the nature of intrafollicular local signalling molecules in the human ovary, we monitored expressed genes of human GCs from preovulatory follicles from IVF‐patients. Surprisingly, the vesicular acetylcholine (ACh) transporter was found; a result leading to identification of a cholinergic system of the antral follicle: Thus ACh is produced by GCs and muscarinic ACh receptors (MR) are present in their membranes. MR‐activation increases proliferation rate and disrupts gap junctional communication. It also elevates intracellular calcium levels, opens a calcium‐activated potassium channel (BKCa) and causes membrane hyperpolarization. The latter event would allow activation of other voltage‐dependent ion channels (e.g. Kv4.2; calcium‐, sodium‐channels). Interference with the chain of these events causes altered steroidogenesis. Further neuronal characteristics of the non‐neuronal GCs (e.g. SNAP25, NCAM) and indication of the presence of a GABAergic system as well, favour the potential importance of intrafollicular signalling systems with ACh being currently the best understood of an emerging class of messenger molecules. (Supported in parts by DFG)