Activation of inositol phosphate formation by circulating noradrenaline but not by sympathetic nerve stimulation with a similar increase of glucose release in perfused rat liver
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Media type:
E-Article
Title:
Activation of inositol phosphate formation by circulating noradrenaline but not by sympathetic nerve stimulation with a similar increase of glucose release in perfused rat liver
Contributor:
PÜSCHEL, Gerhard P.;
JUNGERMANN, Kurt
Description:
<jats:p>In the isolated rat liver perfused <jats:italic>in situ</jats:italic>, stimulation of the nerve bundles around the hepatic artery and portal vein caused an increase of glucose and lactate output and a reduction of perfusion flow. These changes could be inhibited completely by α‐receptor blockers. The possible involvement of inositol phosphates in the intracellular signal transmission was studied.</jats:p><jats:p>
<jats:list list-type="explicit-label">
<jats:list-item><jats:p>In cell‐suspension experiments, which were performed as a positive control, noradrenaline caused an increase in glucose output and, in the presence of 10 mM LiCl, a dose‐dependent and time‐dependent increase of inositol mono, bis and trisphosphate.</jats:p></jats:list-item>
<jats:list-item><jats:p>In the perfused rat liver 1 μM noradrenaline caused an increase of glucose and lactate output and in the presence of 10 mM LiCl a time‐dependent increase of inositol mono, bis and trisphosphate that was comparable to that observed in cell suspensions.</jats:p></jats:list-item>
<jats:list-item><jats:p>In the perfused rat liver stimulation of the nerve bundles around the portal vein and hepatic artery caused a similar increase in glucose and lactate output to that produced by noradrenaline, but in the presence of 10 mM LiCl there was a smaller increase of inositol monophosphate and no increase of inositol bis and trisphosphate.</jats:p></jats:list-item>
</jats:list>
</jats:p><jats:p>These findings are in line with the proposal that circulating noradrenaline reaches every hepatocyte, causing a clear overall increase of inositol phosphate formation and thus calcium release from the endoplasmic reticulum, while the hepatic nerves reach only a few cells causing there a small local change of inositol phosphate metabolism and thence a propagation of the signal via gap junctions.</jats:p>