Biol Reprod Keystone Symposia Conference on Frontiers in Reproductive Biology & Regulation of Fertility.
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BOR - Papers in Press, published online ahead of print October 23, 2002.
Biol Reprod 2002, 10.1095/biolreprod.102.007088
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BIOLOGY OF REPRODUCTION 68, 947–953 (2003)
DOI: 10.1095/biolreprod.102.007088
© 2003 by the Society for the Study of Reproduction, Inc.

Embryo

Amino Acid-Permeable Anion Channels in Early Mouse Embryos and Their Possible Effects on Cleavage1

Momoyo Sonoda2,a, Fujio Okamotob, Hiroshi Kajiyab, Yoshihito Inouea, Ko Honjoa, Yoshinari Sumiia, Tatsuhiko Kawarabayashia, and Koji Okabeb

a Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka 814-0180, Japan b Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka 814-0193, Japan

Effects of several Cl- channel blockers on ionic currents in mouse embryos were studied using whole-cell patch-clamp and microelectrode methods. Microelectrode measurements showed that the resting membrane potential of early embryonic cells (1-cell stage) was -23 mV and that reduction of extracellular Cl- concentration depolarized the membrane, suggesting that Cl- conductance is a major contributor for establishing the resting membrane potential. Membrane currents recorded by whole-cell voltage clamp showed outward rectification and confirmed that a major component of these embryonic currents are carried by Cl- ions. A Cl- channel blocker, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), suppressed the outward rectifier current in a voltage- and concentration-dependent manner. Other Cl- channel blockers (5-nitro-2-[3-phenylpropyl-amino] benzoic acid and 2-[3-(trifluoromethyl)-anilino] nicotinic acid [niflumic acid]) similarly inhibited this current. Simultaneous application of niflumic acid with DIDS further suppressed the outward rectifier current. Under high osmotic condition, niflumic acid, but not DIDS, inhibited the Cl-current, suggesting the presence of two types of Cl- channels: a DIDS-sensitive (swelling-activated) channel, and a DIDS-insensitive (niflumic acid-sensitive) Cl- channel. Anion permeability of the DIDS-insensitive Cl- current differed from that of the compound Cl- current: Rank order of anion permeability of the DIDS-sensitive Cl- channels was I- = Br- > Cl- > gluconate-, whereas that of the DIDS-insensitive Cl- channel was I- = Br- > Cl- >> gluconate-. These results indicate that early mouse embryos have a Cl- channel that is highly permeable to amino acids, which may regulate intracellular amino acid concentration.

1 Part of this work was presented at the 53rd Annual Meeting of the Japan Society of Obstetrics and Gynecology, May 12–15, 2001, Sapporo, Japan

2 Correspondence: Momoyo Sonoda, Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku Fukuoka 814-0180, Japan. FAX: 81 92 865 4114; e-mail: momo-s{at}cis.fukuoka-u.ac.jp






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Copyright © 2003 by the Society for the Study of Reproduction.