Wg. Ding et H. Kitasato, SUPPRESSING NA-CELLS( INFLUX INDUCES AN INCREASE IN INTRACELLULAR ATPCONCENTRATION IN MOUSE PANCREATIC BETA), Japanese Journal of Physiology, 47(3), 1997, pp. 299-306
The effects of suppressing Na+ influx on the activity of ATP-sensitive
K+ channels (K(ATP) channel) and intracellular ATP concentration in m
ouse pancreatic beta-cells were studied. Lowering extracellular Na+ co
ncentration brought about a closing of K(ATP) channels. The activity o
f K(ATP) channels was markedly inhibited by the addition of amiloride,
a blocker of Na+/H+-counter transporter. Mannoheptulose completely el
iminated the inhibition otherwise induced by amiloride. Monensin, an e
lectroneutral Na+/H+ antiporter, remarkably increased the activity of
K(ATP) channels. Removing extracellular Ca2+ also caused inhibition of
the channel activity. ATP measurement experiments using isolated isle
ts revealed that the intracellular ATP concentration of islet cells wa
s significantly increased by incubating either with amiloride or a low
Na+ solution. The measurement of fluorescence excited at 360 nm demon
strated that both suppressing Na+ influx and inhibition of Na+/K+-pump
s caused a transient increase in the reduced form of pyridine nucleoti
de. These findings indicate that a decrease in Na+ influx could cause
an elevation in intracellular ATP concentration probably through induc
ing a fall in ATP consumption at the Na+/K+-pump sites.