Potassium Channels in Chara corallina1: CONTROL AND INTERACTION WITH THE ELECTROGENIC H+ PUMP
AUTOR(ES)
Keifer, David W.
RESUMO
Plasmalemma electrical properties were used to investigate K+ transport and its control in internodal cells of Chara corallina Klein ex Willd., em R.D.W. Cell exposure to solutions containing 10 mm KCl caused the potential, normally −250 millivolts (average), to depolarize in two steps. The first step was a 21 millivolt depolarization that lasted from 1 to 40 minutes. The second step started with an action potential and left the membrane potential at −91 millivolts, with a 10-fold reduction in resistance. We suggest that the second step was caused by the opening of K+ -channels in the membrane. This lowered the resistance and provided a current pathway that partially short-circuited the electrogenic pump. Although largely short-circuited, the electrogenic pump was still operating as indicated by: (a) the depolarized potential of −91 millivolts was more negative than Ek (=−42 millivolts in 10 mm K+); (b) a large net K+ uptake occurred while the cell was depolarized; (c) both the electrogenic pump inhibitor, diethylstilbestrol, and the sulfhydryl-reagent N-ethylmaleimide (which increased the passive membrane permeability) further depolarized the potential in 10 mm KCl.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=426305Documentos Relacionados
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