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The
world's most efficient recycling
plant
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In
twenty-four hours, the human kidney produces
about 170 litres of primary urine. Fortunately
most of this is recovered thanks to a series of
cunning mechanisms so that finally only about
one litre of urine leaves the body during this
time. This recycling machinery consists chiefly
of aquaporins - tens of thousands of millions
in a single kidney.
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In 1992
Peter Agre conducted an elegant experiment in which
he kept, in water, frog oocytes into which he had
introduced a membrane protein called CHIP28. After
some minutes the cells containing the protein had
swollen up, while the others were unaffected.
Obviously, the CHIP28 protein was needed for the cell
to be able to let water in - the first water channel
was discovered. Agre renamed the protein aquaporin,
"water pore". Eight years later and jointly with
other research teams he presented the first
high-resolution images of the three-dimensional
structure of this protein.
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Peter
Agre's decisive experiment showed that only
those cells that contain aquaporin (to the
right in the pictures) can absorb water and
swell up.
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