ISSN:
1432-1424
Keywords:
voltage clamp
;
node of Ranvier
;
gating current
;
chemical modification
;
carboxyl groups
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The effect of the carboxyl group activating reagent N-ethoxy-carbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) on the gating current of the frog node of Ranvier was investigated. A 10-min treatment with 2mm EEDQ (in the presence or absence of 10mm ethylenediamine) irreversibly reduced the slope of the on charge-voltage relationQ on(E), shifted its midpoint potentialE mid in the positive direction and reduced the maximum chargeQ on max measured with strong depolarizing pulses. In six experiments, 2mm EEDQ + 10mm ethylenediamine increased the factork (a reciprocal measure of the slope of theQ on(E) curve) from 16 to 22 mV. In five experiments, 2mm EEDQ alone increasedk from 16 to 23 mV. In a single experiment, 5mm EEDQ + 10mm ethylene diamine increasedk from 17 to 31 mV. The reduction in slope suggests that EEDQ decreases the valence of the gating particles or reduces the fraction of the membrane field that they traverse. In addition, EEDQ (which inhibits inactivation of the sodium current.see M. Rack and K.H. Woll,J. Membrane Biol. 82:41–48, 1984) caused a small increase of the off chargeQ off, and a marked increase of theQ off/Q on ratio, i.e. inhibited charge immobilization. Since the effects of EEDQ occurred regardless of the presence or absence of ethylenediamine, they are probably due to crosslinking reactions. The effects of EEDQ were compared with those of the water-soluble carbodiimide EDC. Treatment with 10 or 50mm EDC (plus 10 or 50mm ethylenediamine) caused a smaller increase ofk than treatment with 2mm EEDQ but reducedQ on max by the same amount.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02209141
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