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Dear all,
I am working on the various pharmacokinetic parameters of the drug
using rats, more precisely, MALE WISTAR RATS, as a animal model.
Being my drug a substrate of CYP, I am more concerned about the age
of the animal. Also I confirmed a considerable change in the
pharmacokinetic parameters (such as Cmax as well as AUC) of the drug
when I changed the animal group from weight range of 270-290 gm to
210-240 gm. (Both groups had "adult rats" in terms of age).
I always found the terminology of the adult male rat is accompanied
with body weight and not the age. The adult male rats with
appropriate weight range (Approx. 220-270) are always referred in
most of the pharmacokinetic studies. But to best of my knowledge I
could not get a strong reference where a correlation between the rats
adult hood is correlated with its average normal body weight.
Different scientists have different criterion for selecting the adult
male rats for the study. I came across a very informative reference;
comparing rat's to human's age: How old is my rat in people years?
Nutrition. 21 (2005) 775-777, published by Robert Quinn. In this
communication author has compared rats and human in terms of
different age periods. But I couldn't find the reference which can
correlate the weight aspect of the animal.
I do accept that weight is such a variable phenomenon which get
affected by many of the factors from diet to strain one has used. But
can we atleast define the weight range for the adult male Wistar rats
which can give me a confidence of selecting the rat with sufficient
musculoskeletal maturity.
In short can we categorize adult rats as "young adults" and "Aged
adults" on basis of their weight range?
Thanking you all.
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Use rats that are 12 months old and above however the key thing is
the weight because you can have rats which are 12 months old and are
sick(under-weight)
If they appear in your study then you have to withdraw them anyway.
The bottom line is that you have to always weigh you rats to ensure
that they healthy with normal physiological or biochemical functions.
s.o.o
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hi
i think the age matters definitely.
increase in weight will mean increase in the lean mass as well as fat
mass.
the best way to go about it is to take animals of abt 8-10 weeks.
if you are looking to study kinetics in next few years then pls
monitor the animals for their anthropometry with increaing ages.
normally the animal house care takers are expected to know the
anthropometry of the animals they nurture.
this over a period of time wil give you an exact idea abt the age and
weight corelation
cheers
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The biggest problem is that unlike humans where the preferred age for
kinetic studies is from 17 to 35 years in rats there is currently no
data. Someone has to look at the pharmacokinetics in rats from
probably two weeks up to about two years and come up with the
appropriate recommendation
However I have come across literature where someone has used adult
mice of 12 months for kinetic studies.
Until that is done researchers will keep on gambling with the precise
age of adult rat.
s.o.o
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The following message was posted to: PharmPK
There is another consideration: when we use rats to implant tumors,
the usual range is 150-250 g. Transplanted tumors do not grow well in
larger rats. Too ornery? As Ogwal comments, this is an area in great
need for good science to know what is really a reliable and
reproducible model.
--
Professor Walter Wolf, Ph.D. Distinguished Professor of
Pharmaceutical Sciences
Director, Pharmacokinetic Imaging Program
Department of Pharmaceutical Sciences, School of Pharmacy
Chair, Biomedical Imaging Science Initiative
University of Southern California 1985 Zonal Ave., Los Angeles, CA
90089-9121
E-Mail: wwolfw.-a-.usc.edu
http://www.usc.edu/research/initiatives/bisi/
http://www.usc.edu/schools/pharmacy/faculty_directory/detail.php?id=59
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