Beta Skin Dose question

[10525kfb@ibm.cl.msu.edu (Kristin Erickson)]

Hi, Radsafers!

On the above question, I cannot resist a few comments on the use of the pig
as the animal model.  It is a poor animal model to use for the following
reasons:

1       The skin of the swine is MUCH thicker than that of the human. (They
have hide,          which can be tanned into thick leather!)

2.      Swine have a normal of 9-10 million RBCs/dl. red blood cell count,
rather than the 4-5 million, the normal human range.

3.      Red blood cells in swine are what we would call microcytes in
humans, that is, very tiny.

4.      Red blood cells in swine have much greater fragility than humans,
and lyse upon the smallest of insult.

5.      Swine physiology is not like that of the human in biochemical and
physiological parameters.  Swine are multiple ovulators, humans
monoovulators,   and blood chemistry normal range values differ in many
paramaters from that of humans.

I could probably go on with this list, but anyone who cares to investigate
a little can confirm this and more to rule out swine as an animal model.  A
much better choice would be the canine species.  Most of the blood
composition, chemistry, physiology is very similar to human values.  In
fact,  by examining a Complete blood count differential (a stained smear of
blood) and looking at eosinophils can one determine whether the blood came
from canines or humans under the microscope.  Even the glucose metabolism
cycle is very similar to that of humans, with the only difference being
that their normal in a canine glucose tolerance test is slightly higher.
For much of the research going to a Phase II FDA study, canines are used
because of these similarities.

However, for reproductive physiology, the bovine species is the best animal
model.  Rats, cats, dogs, mice and most of the smaller species, being
multiple ovulators, have very different pituitary, hormone and steriod
physiology.  Bovines have very similar LH, FSH, GnRH, prolactin, and other
reproductive hormone values, and their cycles are very similar in duration
and fluctuations.

This may be a bit more than you all asked for, but it has been needling me
for years.  Of course this is water under the bridge, but it may be useful
for anyone considering future work using animal models in research to
compare to humans.

Comparison of animal species to humans is at best, a tricky endeavor, and
one should be aware of all of these differences before undertaking the
study.  There is much interesting and useful information to be learned with
the use of animals, and they provide a valuable contribution to our
knowledge and protection of health and the environment, when properly used.
But if improperly used, the animal model data can lead to erroneous or
deficient conclusions.

OK, now I have that off my chest, I will leave all of you to your weekends,
which I hope you enjoy!

Regards,

Kristin


All comments herein contained are my own opinions and/or experiences and
are not necessarily those of my employer or institution.

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Kristin Erickson, Radiation Safety Officer       Email: 10525kfb@msu.edu
Office of Radiation, Chemical and Biological Safety
C124 Research Complex-Eng.
Michigan State University
East Lansing, Michigan 48824
Telephone: (517) 355-5008   Fax: (517)353-4871  http://www.orcbs.msu.edu
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