Cobalt activates potassium conductance in the plasma membrane of cultured renal epithelioid (MDCK)-cells.
Cobalt has been shown to stimulate sodium transport across the distal nephron of the newt kidney. The mechanism of this action remained elusive. The present study has been performed to test for effects of cobalt on electrical properties of cultured subconfluent kidney (MDCK)-cells: cobalt (10 microM) leads to a rapid, sustained and reversible hyperpolarization of the cell membrane, paralleled by an increase of the potassium selectivity and a decrease of the resistance. Thus, cobalt increases the potassium conductance of the cell membrane. The half-maximal effect is elicited by approx. 1 microM. At extracellular calcium concentration reduced to less than 0.1 microM, cobalt (10 microM) leads to a transient hyperpolarization, which can be elicited only once. Thus, cobalt enhances the potassium conductance in a calcium dependent way. At higher concentrations (100 microM) cobalt hyperpolarizes the cell membrane only transiently even in the presence of extracellular calcium. Furthermore 100 microM cobalt interferes with ATP-induced hyperpolarization, which is known to result from calcium mediated activation of K+ channels. Thus, 100 microM cobalt may inhibit ATP-stimulated calcium entry into the cell.
Institute for Physiology, University of Innsbruck, Austria.
A
A
Jungwirth
M
M
Paulmichl
F
F
Lang
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology*; D004285:Dogs; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects*; D011188:Potassium / Q000378:metabolism*
D003035:Cobalt; D000255:Adenosine Triphosphate; D011188:Potassium