Anyone very good at the biology of the kidney?

[Blandmum]

I have a specific question on the reabsorption of glucose in the proximal convoluted tubule.

One of my sixth formers wants an answer, I don't teach this bit of the course and my good text book is in school. I think I have the answer, but not 100% sure.....any takers?

I understand the co-transport with Na from the lumen into the cells on the PCT. Is the movement of glucose into the capillary from the PCT cell simple facilitated diffusion down a concentration gradient?

my textbook says glucose is reabsorbed by co-transport in which energy expended by sodium-potassium pump indirectly transports glucose along with Na. Glucose and Na bind to the same carrier molecule in the brush border membrane. Na enters the cell by moving down its electrical and concentration gradients and carries glucose with it.

So yes, sounds about right

"Proximal Convvoluted tubule - bring back amino acids, glucose note active (NaCl) vs passive (water) transport
Glucose is a special case.
(1) ATP is used in a Na+-K+ pump on basolateral cell surface
(2) glucose is cotransported with Na+ on apical cell surface
(3) Cells are joined so there are no other pathways
(4) recovery in capillary is by diffusion"

From here

and the passive facilitated transport protein would be in the other side of the PCT cell, the side away from the brush boarder?

I assume that the movement of plasma in the capillary prevents the build up of glucose in that side, and maintains the concentration gradient?

'glucose... diffuses into the cells of the PCT and are actively transported into the intercellular spaces from where they diffuse into the surrounding cappillaries. The constant removal of theses substances from the cells of the convoluted tubule causes others to enter from the lumem of the tubule by diffusion.'

Do I win a prize for the person with the least to do tonight?

Thnak you for that girls, I though that was the case, but my decent book is in school, and I haven't taught this in years.

I reckon.

But the kidney is my nemesis...

in answer to the thread title, no not very good at kidney biology, but have my A and P book to hand But kinda makes sense

So, there is active co-transport with Na from the lumen into the cell lining the PGT, because there is no real concentration gradient between the two.

But there is a concentration gradient between the PCT and the capillary because the plasma is constantly moving and maintains the concentration gradient. So facilitated diffusion can happen?

and this would explain why there is glucise in the urine of diabetics, because there is insufficient cencentration gradient between the PCT cell and the plasma?

some na reabsorption occurs by diffusion. in diabetes mellitus glucose concentration in both plasma and glomerular filtrate can become very high, glucose not reabsorbed is excreted. glucose in the kidney filtrate increases the osmotic gradient and holds water in the filtrate, this reduces water reabsorption and increases urine volume, causing dehydration and thirst!

"Why an untreated diabetic has glucose in the urine is that this mechanism is saturated and cannot recover all of the glucose filtered from high blood glucose."

From my link.

MB - it is a Friday night, I have had a G&T and am now drinking wine.

And I did teach physiology, but the kidney...there is always something else going on...

And it has been a few years now...

I tend not to teach this part of the course either.

I do all the neuronal stuff, which is much more fun.

But did I get asked about that? Stuff I could answer? NO!

The perils of setting up a discussion board for your sixth formers. The little buggers get you working on a Friday night.

Thinking about it, shouldn't they be out enjoying themselves on a Friday night?

Tell them to go and have some fun MB. Honestly! Teenagers today...

'Bugger off and enjoy yourselves'

LOL