Low extracellular Ca(2+) activates a transient Cl(-) current in chicken ovarian granulosa cells

• Published in: American Journal of Physiology: Cell Physiology Vol. 279; no. 2; pp. C319 - C325
• Main Authors: Qin, W, Rane, S G, Asem, E K
• Format: Journal Article
• Language: English
• Published: United States 01.08.2000
• Subjects: Animals; Calcium - administration & dosage; Calcium - physiology; Chickens; Chloride Channels - drug effects; Chloride Channels - physiology; Extracellular Space - metabolism; Female; Granulosa Cells - drug effects; Granulosa Cells - physiology; Membrane Potentials - drug effects; Membrane Potentials - physiology; Ovarian Follicle - drug effects; Ovarian Follicle - physiology
• ISSN: 0363-6143
• DOI: 10.1152/ajpcell.2000.279.2.c319

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.