At 09:51 AM 11/29/1999 -0800, you wrote:
>I have a couple of questions regarding "foreign"
>proteins.
>
>First, I was under the impression that proteins are
>"disassembled" by our digestive tract into various
>amino acids,
<big snip>

Well, this is largely correct.  One of the functions of
the high acidity of the normal stomache (pH around 2) will
have the effect of starting protein breakdown by activating the protease
pepsin in the stomache.  there are "some" protease (protein "dissembling")
enzymes in the saliva but have a fairly negligible effect.  Within the
small intestine there are several sources
of protease ezymes including what is secreated by the
pancrease and the intestine itself.  These usually do a
good job (with the stomache) of reducing all the protein into
their constituent amino acids and some di- and tri-peptides
(2 and 3 amino acid strings)  the great bulk of these are
transported into the body for normal metabolism by protein
transporters that only accept amino acids and di- and tri-peptides.  The
problem comes in with the immune system.  There
are little talked about structures within the intestine called
Peyer's patches.  Basically these are clumps of lymphoid tissue and they
will "sample" material within the lumen of the intestine, particulary
undigested or incompletely digested
proteins.  This is one of the major the gateways for inclusion
"whole" proteins in the body.  It is a very small percentage of total
protein ingested, but as we know, immune reations do not require great
amounts of antigen.  To confuse you further, there are other known and most
probably unknown trasportes in the intestine that will transport specific
"whole" proteins that make it.  A "famous" one is an IGF-1 receptor.  This is
famous as IGF-1 is a major hormone in cow's milk (particularly those
treated with BST)  turns out that cow IGF-1 is the same as human IGF-1.
Milk has the affect of reducing stomache acidity thus deactivating pepsin
and allowing substancial amounts of IGF-1 to reach the intestine.  It is a
powerful hormone and has some concerned with the consequences....
Normally, protein hormones are denatured enough in the stomache that they
are not active in the intestine.  This is why an oral
insulin is so difficult because 99% is denatured in the stomache before
reaching the intestine where it could be absorbed.

>Along the same lines, why would there be a problem
>with eating grain fed vs. free range animals (besides
>the obvious higher fat content)? How could the adverse
>effect of foreign proteins possibly be transmitted to
>us through a grain fed animal?

I don't think there is a problem but the personal experiences
of some on this list regarding grain fed animals gives me
pause.  I have never seen evidence that grain injested by
beef ends up in the meat to provide some sort antigen.  The
response to grain fed beef may be placebo, or the response to
other factors that grain antigen.  Interesting question tho.

I've probably thoughouly confused you.  This is not an area
of expertise.  Try doing a search on Peyer's patches and see
what you come up with.


   Wade Reeser



>Any info would be helpful.
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