Amino acid-permeable anion channels in early mouse embryos and their possible effects on cleavage.
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.
Sonoda
Momoyo
M
Department of Obstetrics and Gynecology, School of Medicine, Fukuoka University, Fukuoka 814-0180, Japan. momo-s@cis.fukuoka-u.ac.jp
Okamoto
Fujio
F
Kajiya
Hiroshi
H
Inoue
Yoshihito
Y
Honjo
Ko
K
Sumii
Yoshinari
Y
Kawarabayashi
Tatsuhiko
T
Okabe
Koji
K
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004622:Embryo, Mammalian / Q000502:physiology*; D005260:Female; D005942:Gluconates / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D009544:Niflumic Acid / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism
D000596:Amino Acids; D018118:Chloride Channels; D005942:Gluconates; D009579:Nitrobenzoates; D012333:RNA, Messenger; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D009544:Niflumic Acid; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C030691:gluconic acid; D011188:Potassium