Susana Isabel Ferreira da Silva de Sá ESTROGÉNIOS E ...

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The Sv of the RER was also influenced by the phase of
the estrus cycle and by the sex of the animals (F9.60,
P0.002), similarly to what happened with the surface
area of this organelle (F32.51, P0.0005). The Sv and
the surface area were higher in males and in proestrus rats
than in diestrus rats (Fig. 2B). No differences were found in
these parameters between males and proestrus females.
Golgi apparatus
As shown by ANOVA, the Vv of the Golgi apparatus varied
as a function of the sex of the rats and of the estrus cycle
phase (F14.1, P0.0005), similarly to what occurred with
its volume (F17.02, P0.0005). Specifically, the Vv and
the volume of the Golgi apparatus were higher in proestrus
females than in males and diestrus females (Fig. 3A). No
differences were noticed between males and diestrus females
(Fig. 3A).
The Sv and the surface area of the Golgi apparatus
were also dependent on the sex of the animals and on the
phase of the estrus cycle (F6.23, P0.01 and F23.21,
P0.0005, respectively). The Sv and the surface area
were higher in proestrus females than in males and
diestrus females (Fig. 3B). No differences were found in
these parameters between male rats and diestrus females.
Nuclear pores
ANOVA showed that the variations in the number of pores
per unit length of nuclear membrane were dependent on
the sex of the animals and on the phase of the estrus cycle
(F14.3, P0.0005). The density of nuclear pores was
higher in males than in females, and did not differ between
females at different phases of the estrus cycle (Fig. 4).
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DISCUSSION
Earlier studies have revealed that estrogen, when administered
to ovariectomized rats, augments the protein synthesizing
machinery in VMNvl neurons (Cohen and Pfaff,
1981; Carrer and Aoki, 1982; Jones et al., 1985; Erskine
and Miller, 1995). Data obtained in the present study lend
support and extend these observations by showing that the
size of the RER fluctuates across the ovarian cycle in
parallel with the variations in the levels of endogenous
estrogen. Specifically, the volume and the surface area of
the RER increase from diestrus to proestrus, while estrogen
levels rise, and then decrease until the next diestrus,
as estrogen levels decline. Our results also show that the
Vv of the RER is greater in proestrus than in diestrus rats,
which indicates that at proestrus there is a proportionally
larger increase in the volume of the RER than in the
volume of the cytoplasm. The observation that the surface
area and the Sv of the RER undergo a similar estrusrelated
variation denotes that the larger volume of the RER
in proestrus relative to diestrus rats is attributable not to
dilation of the existing cisternae, but to an effective increase
in the extent of the RER membrane and/or in the
number of RER cisternae. Since the ribosomes connected
to the RER membrane are involved in protein synthesis
(Droz, 1973) there are reasons to assume that VMNvl
S. I. Sá and M. D. Madeira / Neuroscience 133 (2005) 919–924
Fig. 3. Graphic representation of the morphometric data obtained
from the Golgi apparatus of VMNvl neurons of male rats, and of female
rats on diestrus and proestrus. Columns represent means and vertical
bars 1 S.D. (A) Vv and volume. (B) Sv and surface area. Tukey’s post
hoc tests: * P0.05, ** P0.005, *** P0.0005, compared with male
rats; P0.05, P0.0005, compared with diestrus rats.
neurons are metabolically more active in proestrus than in
diestrus rats. As a result of the gonadal steroid-induced
changes in the morphology of the RER, the sex differences
in the size of this organelle are not constant across the
estrus cycle. Specifically, although the volume and the
surface area of the RER were 1.5 and 1.8 times larger,
respectively, in males than in diestrus females, no sexrelated
differences could be noticed when females were in
proestrus.
In contrast to the RER, the sex differences in the
volume and in the surface area of the Golgi apparatus
were noticeable only when females were in proestrus. In
particular, the volume and the surface area of this organelle
were approximately 1.5 times larger in proestrus
females than in males, which is in agreement with data
obtained by Ishunina and coworkers (2001) in the human