Biology of Reproduction, Vol 49, 95-103, Copyright © 1993 by Society for the Study of Reproduction

ARTICLES

Membrane currents of porcine granulosa cells in primary culture: characterization and effects of luteinizing hormone

M Kusaka, N Tohse, H Nakaya, T Tanaka, M Kanno and S Fujimoto
Department of Obstetrics and Gynecology, Hokkaido University School of Medicine, Sapporo, Japan.

In ovarian granulosa cells, LH depolarizes the membrane potential and induces steroid production. The membrane currents of porcine granulosa cells in primary culture were studied by means of the whole cell configuration of the patch-clamp technique to investigate whether the ionic channels are involved in the effects of LH. We identified and characterized two types of K+ currents--a transient outward current (Ito) and a delayed rectifier K+ current (IK)--and one Ca2+ current (ICa). Ito and IK were voltage- and calcium-dependent. Both currents were blocked by 4-aminopyridine, a K+ channel blocker, but only IK was sensitive to tetraethylammonium, another K+ channel blocker. ICa was inactivated within 50 ms of the test pulse. Nifedipine and verapamil, L- type CA2+ channel blockers, did not suppress ICa even at a concentration of 10 microM. Tetramethrin (1 microM), a T-type Ca2+ channel blocker, decreased ICa by 38.4 +/- 5.6% (n = 3). These findings suggest that the current may be a T-type Ca2+ current. LH and dibutyryl cAMP, potent stimulants of steroid production, attenuated Ito only by 13.9 +/- 1.8% (n = 7) and 21.0 +/- 1.5% (n = 4), respectively. However, they did not affect IK and ICa. These results indicated that LH does not modulate CA2+ current directly, but it slightly decreased Ito through cAMP elevation. The LH-induced inhibition of Ito may be involved in the depolarizing effect of LH and may play some role in steroid secretion or other functions in granulosa cells.

This article has been cited by other articles:

				L. Kunz, J. S. Richter, and A. Mayerhofer The Adenosine 5'-Triphosphate-Sensitive Potassium Channel in Endocrine Cells of the Human Ovary: Role in Membrane Potential Generation and Steroidogenesis J. Clin. Endocrinol. Metab., May 1, 2006; 91(5): 1950 - 1955. [Abstract] [Full Text] [PDF]

				D. Platano, M. C. Magli, A. P. Ferraretti, L. Gianaroli, and G. Aicardi L- and T-Type Voltage-Gated Ca2+ Channels in Human Granulosa Cells: Functional Characterization and Cholinergic Regulation J. Clin. Endocrinol. Metab., April 1, 2005; 90(4): 2192 - 2197. [Abstract] [Full Text] [PDF]

				A. Agoston, L. Kunz, A. Krieger, and A. Mayerhofer Two Types of Calcium Channels in Human Ovarian Endocrine Cells: Involvement in Steroidogenesis J. Clin. Endocrinol. Metab., September 1, 2004; 89(9): 4503 - 4512. [Abstract] [Full Text] [PDF]

				L. Kunz, A. Thalhammer, F. D. Berg, U. Berg, D. M. Duffy, R. L. Stouffer, G. A. Dissen, S. R. Ojeda, and A. Mayerhofer Ca2+-Activated, Large Conductance K+ Channel in the Ovary: Identification, Characterization, and Functional Involvement in Steroidogenesis J. Clin. Endocrinol. Metab., December 1, 2002; 87(12): 5566 - 5574. [Abstract] [Full Text] [PDF]

				R. O. Arellano, A. Martinez-Torres, and E. Garay Ionic Currents Activated via Purinergic Receptors in the Cumulus Cell-Enclosed Mouse Oocyte Biol Reprod, September 1, 2002; 67(3): 837 - 846. [Abstract] [Full Text] [PDF]

				M. Manikkam, Y. Li, B. M. Mitchell, D. E. Mason, and L. C. Freeman Potassium Channel Antagonists Influence Porcine Granulosa Cell Proliferation, Differentiation, and Apoptosis Biol Reprod, July 1, 2002; 67(1): 88 - 98. [Abstract] [Full Text] [PDF]

				W. Qin, S. G. Rane, and E. K. Asem Basal lamina of ovarian follicle regulates an inward Cl- current in differentiated granulosa cells Am J Physiol Cell Physiol, January 1, 2002; 282(1): C34 - C48. [Abstract] [Full Text] [PDF]

				D. E. Mason, K. E. Mitchell, Y. Li, M. R. Finley, and L. C. Freeman Molecular Basis of Voltage-Dependent Potassium Currents in Porcine Granulosa Cells Mol. Pharmacol., January 1, 2002; 61(1): 201 - 213. [Abstract] [Full Text] [PDF]

				E. K. Asem, W. Qin, and S. G. Rane Effect of basal lamina of ovarian follicle on T- and L-type Ca2+ currents in differentiated granulosa cells Am J Physiol Endocrinol Metab, January 1, 2002; 282(1): E184 - E196. [Abstract] [Full Text] [PDF]

				W. Qin, S. G. Rane, and E. K. Asem Low extracellular Ca2+ activates a transient Cl- current in chicken ovarian granulosa cells Am J Physiol Cell Physiol, August 1, 2000; 279(2): C319 - C325. [Abstract] [Full Text] [PDF]