M. Paolucci et Ip. Callard, CHARACTERIZATION OF PROGESTERONE-BINDING MOIETIES IN THE LITTLE SKATERAJA-ERINACEA, General and comparative endocrinology, 109(1), 1998, pp. 106-118
In this study we report evidence of a [H-3]progesterone-binding moiety
in the liver and oviduct of the little skate Raja erinacea. It is cha
racterized by high affinity, low capacity, and DNA-cellulose-binding a
ctivity. Furthermore Western blot analysis revealed that monoclonal an
tibodies against the chicken progesterone receptor (PR) subunits A and
B cross-reacted with a 110-kDa band in the liver and a 80-kDa band in
the oviduct. When analyzed by DEAE-Sepharose ion-exchange column chro
matography, [H-3]progesterone-binding molecules resolved into two peak
s, one nonadherent and one adherent to the column. The liver adherent
peak eluted in a linear gradient at a NaCl concentration of about 0.07
M and resolved on Western blot as a single band of a 110 kDa. The ovi
duct adherent peak eluted at about 0.14 M NaCl and resolved on Western
blot as a single band of 80 kDa. Competition studies showed that the
progesterone-binding moiety in the cytosol was specific for progestero
ne. On the contrary, the nuclear component is not specific for progest
erone; it also binds testosterone and estradiol 17 beta in the oviduct
, and progesterone, testosterone, dihydrotestosterone, estradiol 17 be
ta, mibolerone, and R5020 in the liver. The [H-3] progesterone-binding
activity was monitored in both liver and oviduct of females in differ
ent reproductive stages. Females were separated into three groups: lay
ing, nonlaying, and immature. [H-3]Progesterone-binding activity level
s were higher in the liver of immature than of nonlaying skates, and i
t was undetectable in laying skates. [H-3]Progesterone binding was hig
her in the oviduct of laying and nonlaying skates than of immature ska
tes. This PR-binding moiety has many characteristics of a true recepto
r: high affinity, low capacity binds to DNA, and cross-reacts with ant
ibodies against chicken PR. However, while the cytosolic form of this
progesterone-binding component was quite specific for P, nuclear extra
cted material was nonspecific. If these progesterone-binding component
s are homologous with the PR A and PR B forms of other vertebrates, as
we believe, it is clear that there are species differences that proba
bly relate to phylogenetic level and physiology of the organism. (C) 1
998 Academic Press.