title: Intracellular ADP activates K+ channels that are inhibited by ATP in an insulin-secreting cell line.
abstract: The effect of ADP on ATP-sensitive K+ channels in the insulin-secreting RINm5F cell line has been investigated with the help of single-channel current recording from saponin-permeabilized cells. ADP (100-500 microM) markedly activates K+ channels when added to the bath solution in contact with the membrane inside. ADP-beta-S cannot mimick this effect. During sustained ATP (500 microM)-evoked inhibition of K+ channel opening, 500 microM ADP markedly and reversibly activates the channels. Conversely ATP markedly reduces the opening probability of ADP-activated channels. It is suggested that the physiological control of K+ channel opening in the insulin-secreting cells is mediated by changes in ATP/ADP ratio rather than being solely determined by the ATP concentration.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000502:physiology*; D002460:Cell Line; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism
chemical_list: D000227:Adenine Nucleotides; D007328:Insulin; D007473:Ion Channels; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D011188:Potassium