Detection of
Estrogenicity by Bioassay on the Mouse Mammary
Gland in Vivo
J. ŠKARDA
Institute
of Animal Physiology and Genetics, Academy of
Sciences of the Czech Republic, Prague, Czech
Republic
Received
April 27, 2000
Accepted October 13, 2000
Summary
The
wide chemical diversity of estrogenic compounds
precludes an accurate prediction of estrogenic
activity on the basis of chemical structure or
radioimmunological assay and thus requires that
the potency of these compounds is defined by
bioassay. The mammary duct growth response in
intact prepubertal and adult gonadectomized
female and male mice of the C3H/Di strain was
used to assess the estrogenicity of synthetic
compounds or their derivatives. The vehicle for
tested compounds should be free of estrogenic and
other hormonal effects. Olive oil or sunflower
oil exerted estrogenic activities and were thus
unsuitable as vehicles for the tested compounds.
The absence of estrogenic activity, high
solubility of different steroid hormones, and the
low incidence of the inflammatory reactions at
the injection site were achieved by using a
vehicle containing benzyl alcohol, benzyl
benzoate, butylhydroxyanisole,
butylhydroxytoluene, ethyl oleate and ethanol.
The bioassay was primarily designed to examine
the effect of tested compounds on mammogenesis.
The duration of hormone treatment was chosen to
be long enough for induction of duct growth but
too short to induce lobuloalveolar
differentiation. Females were treated for 10
days, males for 15 days. The proportional volume
occupied by mammary epithelial structures was
estimated by the modified Chalkley's technique.
The mean coefficient of variation of quantitative
evaluation of 10 different mammary glands
obtained by two operators varied between 3.2 and
17.4 %. The mean coefficient of variation of
quintuplicate determinations of each mammary
gland by one operator was 10.1 %, and 11.1 % by
the other. The correlation coefficient between
results of two operators was 0.994. Estrogens are
primarily defined by their ability to increase
the mitotic activity of female secondary sex
organs. However, our results have shown that
progesterone alone, if administered in a high
dose, stimulates mammary growth in both intact
prepubertal and OV-X female mice similarly as the
synthetic progestatial steroid norethindrone with
inherent estrogenic properties. In contrast,
progesterone alone had no effect, in young intact
or adult castrated males, but norethindrone did
stimulate mammary growth. These results
demonstrated that the mammary gland of males is a
suitable model for estrogen screening.
Key
words
Mammary
gland · Mouse · Estrogenocity · Bioassay ·
Progesterone
Reprint
requests
Josef
Škarda, Institute of Animal Physiology and
Genetics, Academy of Sciences of the Czech
Republic, Přátelství 560, 104 00 Prague
10-Uhříněves, Czech Republic, e-mail: skarda@iapg.cas.cz
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