PLATFORM SESSION 3. OVARY I: PRIMATE AND HUMAN OVARY
Sunday, August 1, 2004
3:00 PM–5:00 PM
Chair: Peter Leung
Co-Chair: Christian Klausen
(22) NON-NEURONAL ACETYLCHOLINE, AN OVARIAN SIGNALING MOLECULE REGULATED BY FSH.
Mayerhofer, Artur 1, Krieger, Annette 1, Proskocil, Becky2, Spindel , Eliot2, Amsterdam, Abraham3, Dissen, Gregory 2, Ojeda, Sergio2, Wessler, Ignaz 4, 1 Anatomisches Institut Ludwig-Maximillians-Universitaet Muenchen, Munich, Germany2 Division of Neuroscience, Beaverton, OR3 Weizmann Institute of Science, Rehovot, Israel4 Universitaet Mainz, Mainz, Germany
ABSTRACT- Cultured granulosa cells (GCs) isolated from preovulatory follicles, produce acetylcholine (ACh) and possess functional muscarinic ACh receptors (M1/5). In human GCs activation results in intracellular calcium signals, activation of a potassium channel, elevation of the transcription factor egr-1, as well as proliferation, associated with blockage of gap junctional communication (see: JCEM 2001:86:349-54; 2002: 87:1362-7; 2002:87:5566-74). These results obtained in cultured GCs raise the possibility that non-neuronal ACh may act as an intraovarian signalling molecule. In order to explore this possibility, we examined by immunohistochemistry ovarian sites of choline acetyltransferase (ChAT), responsible for ACh synthesis. Ovaries of different species and ages (embryonic rat, mouse, including mice null for ChAT; postnatal and adult rat, neonatal and adult rhesus monkey; adult human) were studied. Results obtained show that ChAT-immunoreactivy (IR) is readily seen in all GCs of healthy antral follicles. ChAT-IR further increases concomitantly with the size of the follicle. Since FSH drives growth of antral follicles and GC development, we hypothesized that regulation of ChAT and ACh levels may be a consequence of the actions of FSH. We thus examined effects of FSH on production of ACh in the rat GFSHR-17 cell line, which stabily expresses the FSH receptor. Using an HPLC-assay we found a dose-dependent increase in ACh production. Together with ChAT expression in growing follicles, these results imply that ACh is likely produced in an FSH-dependent manner in growing follicles. In addition, immunohistochemical studies show that M1 receptor protein is expressed in GCs of large, ChAT-positive follicles. We conclude that GCs of growing follicles are producers and targets for ACh. In contrast, ChAT-IR is absent from embryonic and neonatal ovaries and ovarian development in embryonic mutant mice null for ChAT appears normal. In adult ovaries of all species, ChAT-IR is also not seen in small preantral follices. This implies that ACh is not involved in follicular formation or early follicular growth, which occur in an FSH-independent way. We propose that ACh qualifies as a novel intrafollicular signaling molecule, which is regulated by and may mediate actions of FSH in antral follicles.
KEY WORDS: FSH, ovarian signaling molecule, follicle, acetlycholine