ISSN:
1432-1424
Keywords:
Chara corallina
;
K+ channels
;
I/V characteristics
;
leakage current
;
conductance
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Previous current/voltage (I/V) investigations of theChara K+ state have been extended by increasing the voltage range (up to +200 mV) through blocking the action potential with La3+. A region of negative slope was found in theI/V characteristics at positive PD's, similar to that already observed at PD's more negative than the resting level. These decreases in membrane currents at PD's more negative than −150 mV and at PD's close to 0 or positive are thought to arise from the K+ channel closure. Both the negative slope regions could be reversibly abolished by 0.1mm K+, 20mm Na+, more than 10mm Ca2+ or 5mm tetraethylammonium (TEA). The K+ channels are therefore blocked by TEA, closed by low [K+] o or high [Ca2+] o and are highly selective to K+ over Na+. With the K+ channels closed, the remainingI/V profile was approximately linear over the interval of 400 mV (suggesting a leakage current), but large rectifying currents were observed at PD's more positive than +50 mV. These currents showed a substantial decrease in high [Ca2+] o , sometimes displayed a slight shift to more positive PD's with increasing [K+] o and were unaffected by TEA or changes in [Na+] o . The slope of the linear part of theI/V profile was steeper in low [K+] o than in TEA or high [Na+] o (indicating participation of K+, but not Na+, in the leak current). Diethylstilbestrol (DES) was employed to inhibit the proton pump, but it was found that the leakage current and later the K+ channels were also strongly affected.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01870810
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