| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
ARTICLES |
Department of Human Physiology, School of Medicine, University of California, Davis, Davis, California 95616
Address all correspondence and requests for reprints to: Judith L. Turgeon, Ph.D., Department of Human Physiology, University of California, Davis, California 95616. E-mail: jlturgeon{at}ucdavis.edu
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The PR knockout (PRKO) mouse has been a useful model in establishing the primacy of the PR in the female reproductive cycle (14). PRKO mice are anovulatory, lack endogenous or estrogen-induced preovulatory gonadotropin surges, do not respond to male mouse odor with a gonadotropin surge, and do not exhibit GnRH self-priming in vivo (14, 15, 16). These studies clearly establish an essential function for the PR in the female mouse hypothalamo-pituitary circuit, but the specific sites in the circuit and the cellular processes that are compromised in this mouse model remain to be determined.
Our focus has been on the pituitary site, and studies with rat gonadotropes in vitro have established the acute stimulatory action of progesterone on GnRH- and K+-stimulated LH secretion (17, 18, 19) and also progesterone-independent activation of the PR in GnRH self-priming (9, 10). PRKO mouse pituitary cells could provide a useful model for teasing out pathway components, both upstream of PR activation and downstream, leading to augmented LH secretion. The female mouse, in general, has been less well studied than the rat for in vitro pituitary function, but the tendency has been to assume equivalence between mouse and rat. However, in analyzing the consequences of PR ablation to the proportion of gonadotropes in pituitaries from PRKO mice, our comparison studies with cells from wild-type (WT) mice uncovered marked deviations from what is known for rat pituitary cells. In WT mouse pituitaries, for example, we found that not only do all gonadotropes contain nuclear PR, but also all lactotropes as well, and that estrogen up-regulates PR in both cell types (20). This is in sharp contrast to the rat and the monkey in which the PR localizes exclusively to gonadotropes (21, 22, 23).
Our first aim in this work, therefore, was to characterize the LH secretory responses of female WT mouse pituitary cells in culture using protocols that have been used in studies of cultured female rat pituitary cells to examine GnRH self-priming and progesterone augmentation of GnRH- and elevated K+-stimulated LH secretion. Second, we compared these responses in WT mouse cells with those of pituitary cells from PRKO mice.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Pituitary cell culture and secretion protocols
Protocols employed in these experiments were reviewed and
approved by the University of California Davis Animal Use and Care
Administrative Advisory Committee. Adult female WT and PRKO mice
[C57/6/129sv hybrid (14)] were maintained in controlled
light conditions (14-h light, 10-h dark). Mice were ovariectomized
under tribromoethanol anesthesia (24) and maintained for 2
weeks before use. Pituitary glands were removed after
CO2 narcosis and decapitation. Anterior pituitary
tissue was enzymatically dispersed and prepared for cell culture as
described previously (18); the average yield was 1 x
106 anterior pituitary cells per mouse. Cells
were plated at 3 x 105 on Matrigel-coated
15-mm plastic coverslips in 22-mm multiwell plates. Wells were flooded
with MEM containing d-valine and supplemented with 200
µM kanamycin sulfate, 10% FBS that had been
charcoal treated to remove endogenous steroids, and ±0.2
nM E2. Residual steroid
concentrations in the charcoal-treated serum were 3
pM for progesterone and less than 1
pM for E2 as determined by
RIA. Cells were maintained in a humidified atmosphere (37 C) of 5%
CO2 in air; on day 3, media were replenished (day
of plating = day 1).
On day 4, the cells were changed to serum-free MEM containing 1 mg BSA/ml (MEM/BSA) ± E2 as appropriate and plus experimental treatment (time zero). The treatment groups included: cycloheximide (5 µM), progesterone (20 or 200 nM), RU486 (200 nM), ZK98299 (400 nM), or 8-Br-cAMP (1 mM). Once a treatment was added to the medium, it was present for the duration of the experiment. For all groups, successive 15-min incubations were collected before, during, and after challenge pulses of either GnRH or raised extracellular K+ to monitor LH secretion. Samples were stored at -70 C until assayed for LH by RIA as described previously (18). The intra- and interassay coefficients of variation for a pool of medium (obtained from GnRH-stimulated pituitary cells in culture) containing 190 ± 4 ng LH/ml (n = 28 assays) were 4.2% and 1.9%.
Multiple GnRH pulse protocol. Starting at 90 min (unless otherwise indicated), cells were challenged with four 15-min pulses of GnRH at 60-min intervals. GnRH was used at 1 nM except in initial experiments to establish concentration dependence.
Multiple K+ pulses. Starting at 90 min, cells were challenged with four 15-min pulses of 54 mM K+ at 60-min intervals. For these experiments MEM/BSA medium was replaced with medium of similar composition, pH 7.4, that contained 1 mg BSA/ml, 15 µg phenol red/ml, 110 mM NaCl, 5.4 mM KCl, 1.8 mM CaCl2, 1.6 mM MgSO4, 24 mM NaHCO3, 0.8 mM Na2HPO4, and 25 mM glucose; 54 mM K+ medium was prepared by equimolar replacement of NaCl with KCl.
Data analysis
Data are presented as the mean ± SEM. Each
experiment represents a separate pool of dispersed pituitary cells; n
refers to the number of times an experiment was repeated. For LH
secretion in response to pulsatile secretagogue administration, the
integrated secretory response was calculated as the total amount of LH
secreted during the 15-min exposure to a secretagogue plus that
secreted in the subsequent 15 min. All statistical analyses were done
using SigmaStat (SPSS, Inc., Chicago, IL). For multiple
comparisons, differences between groups were determined by ANOVA and
the Student-Newman-Keuls’ method; where differences are indicated as
being significant, P < 0.05. Where appropriate,
difference between two pulses within the same cell population was
determined using the paired t test with the level of
significance noted in the report of the results.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
. To compare secretion
among groups, we analyzed the integrated response to each pulse; data
for the first and third response are shown in Table 1. The presence or absence of
E2 was without effect on the integrated LH
secretory response to the initial GnRH pulse, and the responses to this
pulse are not significantly different between WT and PRKO cells (Table 1). However, by the third hourly GnRH pulse, differences clearly
emerged. In the zero E2 group, the third LH
secretory response in the WT cells increased slightly while the PRKO
response decreased; the first to third pulse differences within each
group were found to be significant using the paired t test
(P < 0.01) (Table 1 and Fig. 1A).
|
|
). By the third hourly pulse, secretion was double that seen in
response to the initial pulse (Table 1) and showed a plateau in the
response at the fourth pulse. PRKO cells in E2
showed only a slight but significant increase in the secretory response
with subsequent pulses, but it was modest compared with WT cells and
not apparent until the third hourly GnRH pulse (Fig. 1B and Table 1).
For both WT and PRKO cells, inhibition of protein synthesis eliminated
the increase in magnitude with subsequent pulses (Fig. 1C).
Cycloheximide, 5 µM, added 30 min before the
initial GnRH pulse, had no significant effect on the first secretory
response, and the response to the third pulse was not different than
that to the first pulse for both WT and PRKO cells (Table 1).
LH response to multiple GnRH pulses: effect of progesterone
We and others have shown that acute progesterone treatment of rat
pituitary cells cultured in the presence of E2
produces a dramatic augmentation of the LH response to GnRH (reviewed
in Ref. 25). In Fig. 2A we
show that WT mouse pituitary cells under similar experimental
conditions also exhibit an augmented response to GnRH pulses with acute
progesterone exposure. When 200 nM progesterone is
introduced 90 min before the first GnRH pulse, the LH secretory peaks
are significantly greater than for the WT control responses; the degree
of augmentation, however, is about half that found for the rat
[1.5-fold (Fig. 2A) vs. 3-fold (18)].
Extending the progesterone pre-incubation time to 150 min did not
further increase the augmentation (data not shown). Acute progesterone
treatment of PRKO pituitary cells had no significant effect on the LH
secretory response to pulses of GnRH (Fig. 2B).
|
. Because of the potential for agonist
activity of RU486, we repeated the experiments with ZK98299, a class I
antagonist that binds PR but prevents its interaction with DNA
(26) and/or interferes with the recruitment of
coactivators (27, 28). As shown in Fig. 3A, 400
nM ZK98299 had no significant effect on either the initial
response or the potentiated secretory response to pulses of GnRH. In
these experiments the PR antagonists were used to block activation of
the receptor in the absence of progesterone.
|
, for comparison, are shown the integrated LH secretory
responses to the first and third pulse of GnRH when 200 nM
progesterone alone is added 90 min before the first GnRH pulse (data
derived from Fig. 2A). When 200 nM RU486 is added 10 min
before the addition of progesterone, RU486 is able to completely block
progesterone’s augmentation of the response to the first GnRH pulse
(Fig. 3B), thus supporting the assumption that RU486 can act as a PR
antagonist under these conditions. Surprisingly, however, RU486 was
unable to block progesterone’s augmentation of the third response; the
secretory response to the third GnRH pulse was not different from that
found for progesterone alone. Mixed agonist/antagonist activity of
RU486 in mouse gonadotropes cannot be ruled out by these experiments,
but these results show marked differences between WT mouse cells and
rat cells under similar experimental conditions (9, 10).
LH response to pulses of elevated extracellular K+
Secretion can be elicited from anterior pituitary cells with
depolarizing pulses of elevated extracellular K+.
Because acute progesterone treatment has been shown to augment
K+-stimulated LH secretion from rat gonadotropes
(17, 19, 29), we next asked whether mouse cells would
respond to this stimulatory action of progesterone when the GnRH
receptor is bypassed. As shown in Fig. 4A, E2-treated WT
mouse cells show repetitive LH secretory episodes in response to hourly
pulses of 54 mM K+. The addition of
progesterone 90 min before the first K+ pulse had
no significant effect on either the peak LH secretory responses (Fig. 4A) or the integrated secretory responses (data not shown). This lack
of an acute stimulatory action of progesterone in WT mouse cells is a
major deviation from the response in rats; when female rat gonadotropes
are subjected to a similar protocol, acute progesterone treatment
results in a doubling of the LH secretory response to
K+ pulses (19).
|
) as well as integrated secretory responses (data not shown). Acute
exposure of PRKO cells to progesterone had no significant effect on the
LH response to elevated extracellular K+ (Fig. 4B).
Effect of cAMP on GnRH- or K+-stimulated LH
secretion
Pulsatile GnRH stimulates an increase in cAMP in female rat
anterior pituitary cultures (9), and one of the
consequences of increased intracellular cAMP is an augmentation of LH
secretion in response to either GnRH or elevated extracellular
K+ (Ref. 30 and reviewed in Ref.
25). We have hypothesized for the rat model that the
augmentation resulting from treatment with a cAMP analog is due, at
least in part, to progesterone-independent activation of the PR
(10). Therefore, we next tested whether a similar protocol
in PRKO cells would lead to an augmented LH secretory response. The
cAMP analog, 8-Br-cAMP, was introduced into the incubation medium of
E2-treated WT or PRKO pituitary cells beginning
90 min before the first pulse of GnRH. The LH secretory responses in
the presence of 8-Br-cAMP shown in Fig. 5
are calculated as a percent of the control response for each pulse in
WT or PRKO cells as appropriate. For WT cells, cAMP significantly
augmented GnRH-stimulated LH secretion by 2- to 3-fold. PRKO cells also
responded to the presence of cAMP with an augmentation of LH secretion,
but the magnitude of the augmentation was significantly less than that
for WT cells at each of the four GnRH pulses (Fig. 5A). These results
are consistent with our previous findings for female rat pituitary
cells in which 8-Br-cAMP pretreatment led to a 2-fold enhancement of
the LH response to a pulse of GnRH (9).
|
). However, unlike the augmented
response to GnRH, cAMP treatment of PRKO cells led to an enhancement of
K+-stimulated LH secretion at each of the four
pulses that was not significantly different than the augmentation found
for WT cells. The absence of a difference between PRKO and WT cells
suggests that the action of cAMP in enhancing depolarization-stimulated
LH secretion is independent of the PR and is consistent with the lack
of effect for progesterone in augmenting
K+-stimulated LH secretion in WT cells. |
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
A focus in our previous studies has been the proximal pathway leading to PR activation, specifically cross-talk between GnRH receptor binding and progesterone-independent activation of the PR in rat pituitary gonadotropes (9, 10). To use the PRKO mouse to address questions regarding specific components in this cross-talk, it first was necessary to test the assumption that the responses of female WT mouse pituitary cells in culture would be essentially identical to that of female rat cells. As presented here, although there was an overall similarity in LH secretory responses between the WT mouse cells and previous reports for the rat, we found divergences that provide possible clues as to different regulatory strategies adapted by mice and rats.
Steroid effects
In vitro estrogen treatment had no effect on the LH
response to an initial pulse of GnRH in WT mouse cells which is
different than that reported by us and many groups for rat cells in
which estrogen increases the responsiveness of cultured pituitary cells
to GnRH (e.g. Refs. 18, 31, 32). Whether this
is related to the reported differential response of GnRH receptors to
ovariectomy in mice and rats (33, 34) was not examined.
Similar to rats, however, when mouse cells were cultured without
E2, they responded to subsequent GnRH pulses with
repetitive LH secretory responses at close to the same level, and, when
E2 was present, mouse cells moved away from the
initial secretion level to show potentiation of the LH secretory
response to subsequent GnRH pulses. Thus, the mouse response pattern
has the characteristics of GnRH self-priming, which has been described
in rats and humans and contributes to the magnitude of the preovulatory
LH surge (25, 35, 36, 37).
In vivo activation of PRs in the hypothalamus and/or pituitary gland is essential for the normal expression of the preovulatory gonadotropin surge in mice (15, 16, 38) and rats (reviewed in Refs. 39, 40). This has been established in vivo in the rat with many approaches, including pharmacological blockade of the PR with RU486 or ZK98299 (41, 42, 43). In the rat, activation of pituitary PRs with acute progesterone treatment results in a several-fold augmentation of the LH secretory response to GnRH, both in vivo and in vitro (reviewed in Ref. 25). As shown in this study, WT mouse pituitary cells also respond to acute progesterone exposure with an augmentation of GnRH-stimulated LH secretion but at a level of potentiation that is about half that for rat cells under similar conditions (18). The specific target genes for PR that are associated with this augmentation are unknown. However, the observation that acute progesterone augments LH secretion in response to K+-stimulated depolarization in rat gonadotropes suggests that the changes do not necessarily involve signaling components associated with the GnRH receptor and may involve steps in the exocytosis pathway (17, 35). In sharp contrast to the rat, LH secretion in response to K+-stimulated depolarization was unaffected by acute progesterone in WT mouse cells. As shown in the current study, the inability of progesterone to modify LH secretion in response to depolarization is consistent with the modest effect progesterone had on LH secretion in response to GnRH in WT mouse cells. A caveat regarding responses to progesterone for mice compared with rats is the difference in PR localization. For the rat, we reported that the PR localizes exclusively to gonadotropes while in the mouse the PR is also found in lactotropes, thus introducing the possibility of paracrine modulation (20, 22).
GnRH self-priming
For rat cells we reported evidence to support the hypothesis that
the pathways for GnRH self-priming and progesterone augmentation
converge at the PR (9, 10). Based on those rat studies,
the expectation was that gonadotropes lacking a PR would not express
GnRH self-priming, and this expectation was bolstered by the report in
PRKO mice by Chappell et al. (16) that PR
activation is obligatory for expression of the GnRH self-potentiation
effect in vivo. The in vitro work reported here
is consistent with the in vivo report in that, following a
priming pulse, WT cells express a potentiated LH response to subsequent
GnRH pulses that is approximately two times the initial LH secretory
response. Also in line with the in vivo results
(16), PRKO cells in vitro appear to be lacking
a potentiated LH response to subsequent GnRH pulses, although in our
studies there was a slight, but statistically significant, increase in
responsiveness by the third GnRH pulse. However, the modest effect of
acute progesterone in WT cells on GnRH-stimulated secretion in
vitro and the absence of an effect on
K+-stimulated secretion led us to question
whether the mechanism for convergence of GnRH signaling with the PR was
similar between rat and mouse.
cAMP
For the rat, an elevation in cAMP can replace the initial pulse of
GnRH in eliciting the potentiated effect on secretagogue-stimulated LH
secretion (reviewed in Ref. 25), and this cAMP action can
be substantially reduced by pharmacological blockade of the PR
(9, 10). Consistent with the suggestion that a cAMP
cascade can link the GnRH receptor and the PR, elevated cAMP was shown
to increase PR- mediated transcriptional activity in transiently
transfected rat pituitary cells (10). Although cAMP or the
cAMP/protein kinase A cascade can have multiple intracellular
targets, for rat gonadotropes we have shown that more than half of the
augmentation of secretagogue-stimulated LH secretion that was a
consequence of elevated cAMP could be eliminated either by inhibiting
RNA synthesis or by blocking the PR. In both cases there was residual
augmentation suggesting an additional, nongenomic action of cAMP in the
aggregate secretory response (9).
Because of these studies in the rat model, it was of interest, therefore, that WT mouse pituitary cells responded to increased cAMP with a 2- to 3-fold augmentation of the LH secretory response to GnRH and that the augmentation associated with cAMP was much reduced in PRKO cells. The reduced extent of augmentation in the PRKO cells is similar to the residual augmentation in rat cells in which the PR is blocked or transcription is inhibited. Although this similarity could be simple coincidence, the results with K+-stimulated LH secretion provide possible insight. With depolarization as the secretagogue, progesterone is without effect in WT cells, and, although cAMP augments LH secretion resulting from K+ pulses, it does so to the same extent in WT and PRKO cells. The lack of a difference in the absence of the PR suggests that with K+ as secretagogue the consequences of cAMP treatment are limited to the events associated with depolarization-stimulated calcium entry and exocytosis. When the secretagogue is GnRH, the demonstration of a difference between WT and PRKO supports the hypothesis that, in this pathway, at least part of the augmenting effect of elevated cAMP is working through the PR.
PR
In studies with rat gonadotropes, a decisive test of the
hypothesis that the GnRH self-priming pathway involves
ligand-independent activation of the PR is that blockade with the PR
antagonist, RU486, eliminates GnRH self-priming in the absence of
progesterone (9, 10). When this test was applied to WT
mouse cells, PR antagonists with two different modes of action, RU486
and ZK98299, failed to prevent potentiation of the LH secretory
responses to multiple GnRH pulses. Although the protocols were
essentially identical to those used earlier with rat cells, it is
possible that factors such as antagonist concentration or temporal
requirements might vary between the rat and the mouse. Another related
consideration is a possible difference in expression of A and B
isoforms between the rat and the mouse. There are no data available for
the mouse pituitary gland, but for mouse uterus it has been reported
that PR-A is the predominant form (44). For rat
pituitaries there is no information on A and B protein, but Szabo
et al. have reported that mRNAs for both isoforms are
expressed, and they appear to be similarly regulated across the estrous
cycle (45). In other systems, PR-A and PR-B have been
shown to have differential transactivation properties, and PR-A can
modulate PR-B transcriptional activity (reviewed in Ref.
46). That this could translate into distinct physiological
functions is shown by a report in mice with ablation of PR-A that PR-B
uniquely regulated a subset of uterine target genes (47).
Recently, it was reported that the isoforms have a differential ability
to efficiently recruit coactivators and corepressors (48).
How this latter point could explain the variations in functional
interactions of PR antagonists with A and B forms remains to be
examined for specific cell contexts. In our work in WT mouse
pituitary cells, however, RU486 was ineffective in blocking
progesterone’s action after multiple GnRH pulses, and neither RU486
nor ZK98299 was able to prevent GnRH self-priming, in contrast to the
action of these PR antagonists in rat pituitary cells. Thus, a tempting
speculation to explain these divergences is that mouse and rat
pituitaries express different ratios of the PR isoforms. In line with
this we found that while progesterone can down-regulate PR
protein in rat and mouse gonadotropes, the progesterone-induced loss in
rats is almost twice that in mice (Ref. 13 and
Turgeon J., G. Shyamala, and D. Waring,
unpublished observation). Progesterone-dependent degradation of the PR
in rats was shown to occur through a proteasome pathway, and it remains
to be determined whether the availability of different PR isoforms as
substrates for this pathway are affected by, for example,
variations in the composition of multicomponent transcription complexes
specific to the context of gonadotropes.
In summary, we show that, while LH secretion from cultured female WT mouse gonadotropes exhibits a general similarity to rat cells, there also are marked differences. Particularly noteworthy are the inconsistencies in the responses in the mouse with those for the rat as a model of the GnRH self-priming pathway and its convergence with the PR. WT mouse cells were similar to rat cells in that they showed an E2-dependent potentiated LH secretory response to multiple GnRH pulses similar to GnRH self-priming, and, as predicted by the hypothesis for convergence with the PR, GnRH self-priming was greatly attenuated in PRKO cells. However, the response of WT cells to acute progesterone was a modest augmentation of GnRH-stimulated LH release that was about half that reported for rats and was absent with K+ as secretagogue, suggesting possible differences in targets for PR in the secretory pathway in mouse gonadotropes. Similar to reports for rat cells, increased cAMP was able to substitute for the GnRH priming pulse. However, this occurred with PRKO cells as well but at a reduced level, indicating that at least part of the action of increased cAMP is independent of the PR. In a significant divergence from the rat, pharmacological blockade of the PR did not interfere with GnRH self-priming in WT mouse cells and only partially prevented the augmentative action of progesterone. These data suggest that mouse gonadotropes have adapted different strategies for amplifying the GnRH signal. Additional studies are required to resolve the apparent inconsistencies, but we speculate that the mechanisms underlying these strategies involve, at least in part, differences in PR isoform expression.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
Received February 22, 2001.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  H. J. Kim, M. C Gieske, S. Hudgins, B. G. Kim, A. Krust, P. Chambon, and C. Ko Estrogen receptor {alpha}-induced cholecystokinin type A receptor expression in the female mouse pituitary J. Endocrinol., December 1, 2007; 195(3): 393 - 405. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. W. Waring and J. L. Turgeon Estradiol Inhibition of Voltage-Activated and Gonadotropin-Releasing Hormone-Induced Currents in Mouse Gonadotrophs Endocrinology, December 1, 2006; 147(12): 5798 - 5805. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L Turgeon and D. W Waring Differential expression and regulation of progesterone receptor isoforms in rat and mouse pituitary cells and L{beta}T2 gonadotropes. J. Endocrinol., September 1, 2006; 190(3): 837 - 846. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. E Sanchez-Criado, J. C Garrido-Gracia, C. Bellido, R. Aguilar, P. Guelmes, P. Abreu, R. Alonso, I. Barranco, Y. Millan, and J. M. de las Mulas Oestradiol-17{beta} inhibits tamoxifen-induced LHRH self-priming blocking hormone-dependent and ligand-independent activation of the gonadotrope progesterone receptor in the rat. J. Endocrinol., July 1, 2006; 190(1): 73 - 84. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.L. Crawford, J.R. McNeilly, and A.S. McNeilly No Evidence for Pituitary Priming to Gonadotropin-Releasing Hormone in Relation to Luteinizing Hormone (LH) Secretion Prior to the Preovulatory LH Surge in Ewes Biol Reprod, July 1, 2004; 71(1): 224 - 235. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Turgeon, G. Shyamala, and D. W. Waring PR Localization and Anterior Pituitary Cell Populations in Vitro in Ovariectomized Wild-Type and PR-Knockout Mice Endocrinology, October 1, 2001; 142(10): 4479 - 4485. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
