The pancreas detects the glucose in the blood and releases insulin from the B-cells.  This is a fascinating process because without glucose, insulin can not be released, and without insulin, glucose can not be removed from the blood.

The mechanism of this release is simply amazing to me.  There are so many fascinating intricate details and it reminds me of falling dominoes, on thing happens and a beautiful cascade of other processes happen to eventually release insulin for its mission.

Step 1 When blood sugar is raised (due to ingesting carbohydrates), glucose is transported in the blood into B-cells of the pancreas through the GLUT 2 transporter.  The CLUT2 transporter is a hexose low affinity, high capacity “glucose sensor”, meaning that it will allow glucose to be moved into the B-cells in a large number.

As it moves into the cell, glucose is phosphorylated by glucokinase.

cellphosglu2

Step 2 The phosphorylation of the glucose molecules causes the ATP:ADP ratio to increase (because of glycolisis).  The cells contain an special ATP sensitive potassium channel.  When the ATP is raised, the channel opens and releases potassium into the cell.

cellphosglupotas1

Step 3 Higher levels of potassium in the cell causes depolorization of the cell membrane.  This depolorization causes the voltage-gated calcium channel to open, allowing calcium ions to flow in to the cell.

cellphosglupotascal1

Step 4 This increase in cellular calcium causes the release of insulin from the storage granule.

cellphosglupotascalinsrelease

After glucose has been taken up out of the blood, the pancreas turns off insulin production.  The release of insulin is a biphasic release.  The initial release happens about 10 minutes after food is ingested.  This release is quick and an “emergency, emergency!!” release so that the toxic glucose is removed from the blood as quickly as possible.  This is where what has been stored is released.  The secondary release happens later after more insulin is synthesized and processed.

I am hoping to get a better understanding on the process of this second release and when and why the sythesis initiated.  I will post back if I am able to find more information.

Insulin Post Table of Contents

Advertisements