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, Wuxuan, Rane, Stanley G., Asem, Elikplimi K.
• Format: Journal Article
• Language: English
• Published: 01.08.2000
• ISSN: 0363-6143; 1522-1563
• 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.