Exp Clin Endocrinol Diabetes 2007; 115 - OR08_3
DOI: 10.1055/s-2007-972247

Ovarian KCNQ channels and regulation by non-neuronal acetylcholine: Modulation of human granulosa cell proliferation and steroidogenesis

L Kunz 1, C Roggors 1, A Mayerhofer 1
  • 1Anatomisches Institut der LMU am Biederstein, München, Germany

Objectives: Non-neuronal acetylcholine (ACh) is about to be recognised to play an important part in the human ovary, e.g. muscarinic stimulation enhances proliferation of human granulosa cells (GCs). ACh affects ion channels in the human ovary as well. We reported opening of a Ca2+-activated K+ channel (BKCa) and cessation of intercellular communication via gap junctions (GJs) as a consequence of muscarinic stimulation of human GCs. In addition we have now observed the reversible inhibition of a K+ current by the ACh analogue carbachol in patch-clamp recordings. This current was characterised and its cellular role investigated.

Methods: Human GCs obtained from in vitro fertilisation patients were cultured. Whole-cell K+ currents were recorded utilising the patch-clamp technique. Cell proliferation and progesterone production were measured using commercial assays.

Results: The ACh-sensitive current is reminiscent of a so-called M-current described in neuronal systems, which is carried by KCNQ channels and blocked by muscarinic stimulation as well. In accordance, we detected mRNAs encoding KCNQ 1, 4, and 5, but not the neuronal types KCNQ 2 and 3. KCNQ 1 protein was found in GCs of large ovarian follicles using immunohistochemistry. The current is sensitive to the specific KCNQ blocker XE991, which also blocked gonadotropin (hCG)-stimulated progesterone production and increased cell proliferation, respectively.

Conclusion: KCNQ channels are blocked by the mitogenic signalling molecule ACh, and blockage of KCNQ channels by XE991 entails GC proliferation. Therefore, we suggest that KCNQ channels, in collaboration with GJs, mediate the proliferative action of intraovarian ACh. Furthermore, mutations of KCNQ channels cause severe channelopathies (e.g. LQT syndrome). We, thus, speculate that KCNQ mutations in GCs might be involved in ovarian dysfunctions. The multitude of regulatory effects of ACh on ion channels in human GCs (KCNQ closing, GJ closing, BKCa opening) emphasises the complexity of actions of this intraovarian signalling molecule.