Inhibition of Ca2+-dependent K+ channels by lead in one-step inside-out vesicles from human red cell membranes.
Pb2+ modified the apparent threshold sensitivity to Ca2+ of individual K+ channels with a biphasic time-course. At first, the sensitivity to Ca2+ was lowered with the result of a decrease of the fraction of activated vesicles at a given Ca2+ concentration. Later, Pb2+ increased the sensitivity to Ca2+ and the fraction of activated vesicles. The increase of Pb2+ concentration increased the extent of the initial inhibition but decreased its duration. The inhibitory effect was not observed when the addition of Ca2+ preceded the addition of Pb2+. The presence of Mg2+ in the incubation medium was also required. In the absence of Mg2+, Pb2+ decreased the rate of uptake of 86Rb, but no decrease in the fraction of activated vesicles could be demonstrated.
J
J
Alvarez
J
J
García-Sancho
B
B
Herreros
D002118:Calcium / Q000097:blood*; D002122:Calcium Chloride / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007854:Lead / Q000494:pharmacology*; D008274:Magnesium / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D012413:Rubidium / Q000378:metabolism; D013997:Time Factors
D007473:Ion Channels; D009566:Nitrates; D007854:Lead; C017461:lead nitrate; D008274:Magnesium; D002122:Calcium Chloride; D012413:Rubidium; D011188:Potassium; D002118:Calcium