ischaemic preconditioning of the human heart. - Leicester Research ...

sensitive G-protein (Gi, see Figure below) [ 1691. The G protein activation pathway may
modulate the sensitivity of the Kxn, channel to inhibition by ATP, so acting via a similar
manner to the metabolic regulators [143]. The activity of KATP channels can also be
modulated by phosphorylation, which might come about by activation of protein kinase C
(PKC) [9].
Other factors that influence the state of the K.
\ý, -,, channel include the binding of Mg2+
salts of nucleoside diphosphates (NDP) , such as Mg ADP and Mg GDP to an activating
site on the channel. The activating site is different from the inhibitory ATP site.
Therefore the opening of K. yI. 1, channels is regulated by the quotient of ATP/NDP [9].
extracellular
Noradrenalinc
Gi
oy
GDP
GTP
The physiological role of the K. \.,,,, channels depends on the tissue. Those found
in pancreatic P-cells determine the resting membrane potential and regulate insulin
release in response to the plasma glucose levels. When glucose is taken up by the
pancreatic P-cells, this causes an increase in ATP concentration near the channel, so
closing the K.,
\.,.,, channel which depolarises the 0-cell and leads to Ca2+ entry into the
cell via voltage-gated calcium channels , so inducing insulin secretion [9]. In many
21
KATI'channel
initochondrial