Low extracellular Ca(2+) activates a transient Cl(-) current in chicken ovarian granulosa cells.
The effects of low Ca(2+) on ion currents in hen ovarian granulosa cells were examined. A fast activating and inactivating transient outward current (TOC) and a slowly activating outward current (SOC) could be observed. In the presence of normal Ca(2+) concentration (2. 5 mM) and with a holding potential of -80 mV, SOC was activated in all cells with command pulses more positive than -20 mV. In 2.5 mM Ca(2+), TOC appeared in 10% of cells at the command pulse of +80 mV and in 60-85% of cells at +100 to +120 mV. In low-Ca(2+) solution and command potential of +80 mV (holding potential of -80 mV), the amplitude of TOC was enhanced in cells that expressed it in normal Ca(2+), and TOC appeared in 43% of the cells that did not express it initially in normal Ca(2+). At both normal and low Ca(2+) levels, TOC decreased as the holding potential became more positive. TOC was reduced in Cl(-)-deficient solution and in the presence of 5-nitro-2-(3-phenylpropylamino)benzoic acid, a Cl(-) channel blocker. These findings suggest that chicken granulosa cells express a Ca(2+)-inactivated TOC carried by Cl(-). This current may serve as a signal for some of the reduced metabolic functions of granulosa cells associated with Ca(2+) deficiency.
Department of Basic Medical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, Indiana 47907-1246, USA.
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D000818:Animals; D002118:Calcium / Q000008:administration & dosage / Q000502:physiology*; D002645:Chickens; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology
D018118:Chloride Channels; D002118:Calcium