Lecture 6 and 7 Flashcards
In the absence of glucose, net sodium absorption…
decreases- this is the first bit of evidence to show a link between sodium and glucose absorption.
What does DNP do?
Uncouples mitochondria so stops ATP production.
What did DNP do to net sodium absorption?
Decreased it to nearly zero, showing that the sodium and glucose movement requires energy.
What does ouabain do?
Blocks the Na+/K+ ATPase.
Net glucose absorption is dependent on the presence of extracellular ….
sodium
How to make brush border membrane vesicles?
homogenise tissue from the intestine, centrifuge to separate the two membranes.
Describe a brush border membrane vesicle.
The outside of the vesicle represents the lumen and the inside represents the intracellular compartment. We can change both environments to mimic absorption across the apical membrane.
The overshoot is typical of a …
carrier mediated transport process
L-glucose movement is…
passive
D-glucose movement is…
carrier mediated
Phlorizin is a…
inhibitor of the D-glucose carrier mediated transport process.
As well as D-glucose, what is also a substrate of SGLT1?
D-galactose
What is not a substrate of SGLT1?
D-fructose and L-glucose.
What experiment identifies the tissues in which SGLT1 is expressed?
Northern blot
Where did the northern blot identify SGLT1?
Duodenum, jejunum, ileum, kidney and lungs.
What technique identifies where in the tissue the transporter is expressed?
Immunostaining.
What stain identifies the nucleus?
DAPI
Can a patient with GGM syndrome absorb fructose?
Yes, they have a problem with SGLT1 which does not transport fructose.
The D28N mutation of SGLT1 means the protein is…
missorted and not trafficked to the membrane.
Immunostaining of the SGLT1 with the C292Y mutation shows the protein is…
trapped between the nucleus and the membrane
Lactase deficiency causes…
Diarrhoea, intestinal cramps and flatulence.
How is lactase deficiency treated?
With removal of milk products from diet or food treated with commercial lactase.
How can lactase deficiency be identified/diagnosed?
Hydrogen breath test.
Why is hydrogen tested?
Hydrogen is a gas produced by bacteria in the colon when they break down carbohydrates. Carbohydrates shouldn’t reach the colon in normal people as it should all be absorbed in the small intestine.
How does the hydrogen get to the lungs?
50% of the hydrogen produced by the bacteria is absorbed and transported to the lungs and excreted.
