Pfaller_and_Gstraunthaler_1998 - reactive intermediates can...

Nephrotoxicity Testing in Vitro-What
We
Know and What
We
Need
to
Know
Walter Pfaller and
Gerhard Gstraunthaler
Institute of Physiology, University of Innsbruck, Innsbruck, Austria
The kidney is affected by
many
chemicals. Some of the chemicals
may even
contribute
to
end-
stage
renal disease and thus contribute considerably
to
health
care
costs.
Because of the large
functional
reserve
of the kidney, which masks signs of
dysfunction,
early
diagnosis
of renal
disease is often difficult.
Although
numerous
studies aimed
at
understanding the mechanisms
underlying chemicals and drugs that target various renal cell
types
have delivered enough
understanding for
a
reasonable risk
assessment,
there is still
an
urgent
need
to
better understand
the mechanisms leading
to
renal cell injury and
organ
dysfunction. The increasing
use
of in vitro
techniques using isolated renal cells, nephron fragments,
or
cell cultures derived from specific
renal cell
types
has improved
our
insight into the molecular mechanisms involved in nephrotoxicity.
A short overview is given
on
the various in vitro
systems
currently used
to
clarify mechanistic
aspects
leading
to
sublethal
or
lethal injury of the functionally
most
important nephron epithelial
cells derived from various species. Whereas freshly isolated cells and nephron fragments
appear
to represent
a
sufficient basis
to
study
acute
effects
(hours)
of
nephrotoxins,
e.g., on
cell
metabolism, primary cultures of these cells
are more
appropriate
to
study long-term effects. In
contrast to
isolated cells and fragments, however, primary cultures tend
to
first lose several of
their in vivo metabolic properties during culture, and second
to
have only
a
limited life
span
(days
to
weeks). Moreover, establishing such primary cultures is
a
time-consuming and laborious
procedure. For that
reason
many
studies have been carried
out
on
renal cell lines, which
are easy
to
cultivate in large quantities and which have
an
unlimited life
span.
Unfortunately,
none
of the
lines display
a
state
of differentiation comparable
to
that of freshly isolated cells
or
their primary
cultures. Most often they lack expression of key functions (e.g., gluconeogenesis
or
organic anion
transport) of their in vivo correspondents. Therefore, the
use
of cell lines for
assessment
of
nephrotoxic mechanisms will be limited
to
those functions the lines
express.
Upcoming molecular
biology approaches such
as
the transduction of immortalizing
genes
into primary cultures and the
utilization of cells from transgenic animals
may
in the
near
future result in the
availability of highly
differentiated renal cells with markedly extended life
spans
and
near
in vivo
characteristics that
may
facilitate the
use
of renal cell culture for routine screening of nephrotoxins.