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Glucose Transporter

Matt Jones jonesmat at ohsu.edu
Tue Nov 16 13:21:58 EST 1999


In article <80o48f$lb6$1 at nnrp03.primenet.com> Rowland Jenkins,
rjenkin at primenet.com writes:
>Maybe someone can help me out with this. I haven't been able to find the
>number of glucose transporters per unit area of membrane (facilitated
>transport). Is this known at all?
>

This information is often hard to come by because it involves several
independent kinds of measurements. First, you need to know the area of
the membrane that's being studied. Because membranes are often
convoluted, it's hard to measure this with a microscope. So instead one
often uses patch clamp measurements of membrane capacitance (which is
proportional to area). Next, you need to have some estimate of
transporter number in the same cell. The easiest way would be to do
single cell radiolabeled glucose binding, and get a Bmax value -in the
same cell- that the capacitance measurement came from. For most cells,
there aren't enough transporters to get a decent binding signal from a
single cell. One can obtain this in oocytes sometimes, because they're so
huge. But then the density information comes from a cell that is probably
-not- the cell you're really interested in (unless you're really studying
glucose transport in the oocyte membrane).  An alternative is to measure
the transport current (if the transporter is electrogenic). If you know
the current generated by a single transporter (a whole thesis project in
itself), then the whole-cell transporter current can be coupled with the
capacitance measurements to give an estimate of transporter density. I
don't know if the glucose transporter is electrogenic or not. But I would
suggest doing a medline search to incorporate some of these methods, like
search for "glucose" AND "transporter" AND "capacitance" OR "current".

Cheers,

Matt Jones




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