[Dioxin-l] threshold dose?

[Henshel, Diane S.]

Just out of curiosity, why does everyone say that dioxin is
"indestructable".
All evidence I know of is that metabolism is very slow, but by no means
non-existent.  Quite the contrary, Ross Norstrom's latest endeavors show
many metabolites present in the bodies of wildlife.  The question, though,
is what is the biological/toxicological activity of these metabolites, as
the PCB metabolites are also toxic/biologically active, for example.

> -----Original Message-----
> From:	Jon Campbell [SMTP:jon@cqs.com]
> Sent:	Sunday, February 13, 2000 9:57 PM
> To:	david bell; dioxin-l@venice.essential.org
> Subject:	Re: [Dioxin-l] threshold dose?
> 
> David,
> 
>      Do you have documentation on this? This is contrary to the published
> data on the receptor/dioxin binding that I have read up to this point.
> 
> Jon
> ----- Original Message -----
> From: "david bell" <burnt_paper@hotmail.com>
> To: <dioxin-l@venice.essential.org>
> Sent: Sunday, February 13, 2000 3:29 AM
> Subject: Re: [Dioxin-l] threshold dose?
> 
> 
> > > >4. Since dioxin is indestructible in the human body, and since dioxin
> > > >molecules are extremely tenacious at the hormone receptor site (the
> > >normal
> > > >hormone destructor enzyme appears to have no effect) the gene
> continues
> > >in
> > > >an unusual ON or OFF state for the life of the cell.
> >
> > One of the things that has just become clear recently is that the
> activated
> > dioxin receptor (AhR) is destroyed (>90%) within one hour, even if
> dioxin
> is
> > the activating agent. That is not to say the dioxin is destroyed, but
> the
> > active receptor is- and so it stops signalling very rapidly.
> >
> > This starts to explain some of the differences between polycyclic
> aromatics
> > (PAHs), and dioxin- the AhR is switched on for just long enough to
> destroy
> > the PAHs- at which point the AhR is all destroyed, and no more PAH is
> > available to switch on the AhR. By contrast, if there is a sufficient
> amount
> > of dioxin, it just keeps on activating newly synthesised AhR protein.
> >
> > cheers
> > david
> >
> > (Degradation of the basic helix-loop-helix/Per-ARNT-Sim homology domain
> > dioxin receptor via the ubiquitin/proteasome pathway Roberts_BJ,
> Whitelaw_ML
> > JOURNAL OF BIOLOGICAL CHEMISTRY, 1999, Vol.274, No.51, pp.36351-36356).
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> 
> 
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