[Calcium-dependent chloride channels in plasma membrane of oocytes from toad, Bufo bufo gargarizans].
In this paper, membrane current properties of the fully-grown oocytes from toad, Bufo bufo gargarizans, were studied by using two-microelectrode voltage clamp technique. Axion of adult female toad was destroyed, and then ovarian lobes containing oocytes in stage I to VI were removed and incubated in Ca(2+)-free ND96 solution with collagenase (1.5 mg/ml) for 1 h. Subsequently, the oocytes were washed in Ca(2+)-free ND96 solution for 10 min to completely remove the follicular layer. For the experiments only the oocytes in stage V and VI were selected and used during 1 to 5 d. The membrane was depolarized from a holding potential of -80 mV to +60 mV in 10 mV step. It was found that a sustained outward current was elicited by depolarization. Potassium channel blockers (tetraethylammonium chloride, TEA, 10 mmol/L and 4-aminopyridine, 4-AP, 10 mmol/L) reduced the outward current to (23.4+/-0.72)% of the maximum. However, further addition of chloride channel blocker (5-nitro-2, 3-phenypropylamino benzoate, NPPB, 30 micromol/L) could almost completely block the outward current to (2.1+/-0.08)% of the maximum. In the presence of TEA and 4-AP, removal of extracellular Ca(2+) or adding verapamil (40 micromol/L), could also reduce the outward current to (2.2+/-0.04) % and (3.1+/-0.15) % of the maximum, respectively. It is concluded that calcium-dependent chloride channels exist in plasma membrane of Bufo bufo gargarizans oocytes, besides potassium channels.
Pi
Yan-Li
YL
Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan 430080, China.
Ma
Ji-Hua
JH
Zhang
Pei-Hua
PH
Duan
Jing-Jing
JJ
D015761:4-Aminopyridine / Q000633:toxicity; D000818:Animals; D002023:Bufo bufo; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D005260:Female; D009579:Nitrobenzoates / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D018118:Chloride Channels; D009579:Nitrobenzoates; D013757:Tetraethylammonium Compounds; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D015761:4-Aminopyridine; D014700:Verapamil; D002118:Calcium