Full text of DOI:10.1007/BF03343939

J. Endocrinol. Invest. 24: RC31-RC33, 2001
RAPID COMMUNICATION
Growth hormone-inhibiting activity of cortistatin in the rat
R. Deghenghi*, R. Avallone**, A. Torsello**, G. Muccioli***, E. Ghigo****, and V. Locatelli**
*Europeptides, Argenteuil, France; **Department of Experimental and Environmental Medicine and Biotechnologies,
University of Milano-Bicocca, Milan, and ***Departments of Anatomy, Pharmacology and Forensic Medicine, and
****Internal Medicine, University of Turin, Turin, Italy
ABSTRACT. Cortistatin-14 (CST-14) is an endogenous neuropeptide with notable structural simi-
larities to native somatostatin-14 (SS-14), but different physiological functions. Differences in the phys-
iology of the two peptides do not provide conclusive evidence for a specific receptor for CST. To date,
the effects of CST-14 on anterior pituitary hormones have never been reported. Aim of this study
was to investigate the in vivo effects of CST-14 on GH secretion in comparison to SS-14. Our results
demonstrate that CST-14 was very effective in reducing GH secretion in normal male anaesthetized
rats. Its activity was similar to that of SS-14 and had a rapid onset and a slightly longer duration of ac-
tion. In conclusion, we have reported for the first time that CST is a potent and effective inhibitor of
GH release in rats and that its action may be mediated by the interaction with one or different SS re-
ceptor subtypes.
(J. Endocrinol. Invest. 24: RC31-RC33, 2001)
©2001, Editrice Kurtis
INTRODUCTION
tagogues (GHS) in human pituitary membranes (5). It is
therefore of importance to investigate the in vivo effects
of CST-14 in comparison with SS-14 in search of a cor-
relation between binding and biological activities of these
natural neuropeptides on the endocrine system, an aspect
so far neglected.
Cortistatin-14 (CST-14) is an endogenous neuropeptide
endowed with many analogies to native somatostatin-14
(SS-14) but with a restricted brain cortical expression and
different pharmacological profile (1). CST-14 shares 11
amino acids with SS-14 and was shown to bind with sim-
ilar affinities to all five cloned human SS receptor subtypes
expressed in transfected cell lines (2). However, differ-
ently from SS, CST induces slow-wave sleep, reduction of
locomotor activity, and activation of cation selective cur-
rents not responsive to SS (3). Expression of mRNA en-
coding CST follows a circardian rhythm and is up regu-
lated on deprivation of sleep, suggesting that CST might
act as a sleep modulatory factor (4). However, the differ-
ences in SS and CST physiology do not provide conclu-
sive evidence for CST specific receptors. Whether CST
effects are mediated via SS and/or a CST specific recep-
tor(s) still remains to be determined. Interestingly, it has
recently reported that CST-14 and some synthetic SS oc-
tapeptide analogs (mainly lanreotide and vapreotide), but
not SS-14, may interact with the receptor for GH secre-
MATERIALS AND METHODS
Chemicals
All peptides reported in this paper have been synthetized by
conventional solid phase synthesis. Each peptide was puri-
fied to at least 98% purity by high-performance liquid chro-
matography.
Animals
Male Sprague-Dawley rats weighing 300-350 g [Charles
River, Calco (Lecco), Italy] were housed in our facilities un-
der controlled conditions (22 C, 65% humidity, artificial
light from 06:00-20:00 h). A standard dry diet and water
were available ad libitum. All the experiments were per-
formed in accordance with the Italian guidelines for the use
of animals in medical research.
Experimental procedure
Key-words: Cortistatin, somatostatin, growth hormone, pituitary receptors,
On the day of the experiment, rats were deeply anaes-
thetized with ketamine hydrochloride (58 mg/kg, ip) and
xylazine (12 mg/kg, ip) and then treated sc with graded dos-
es (40, 80, 160, and 320 μg/kg) of CST-14 or SS-14 or iso-
volumetric amounts of physiological saline. Blood samples
growth hormone secretagogues.
Correspondence: Prof. Vittorio Locatelli, Dipartimento di Farmacologia,
Università di Milano, Via Vanvitelli 32, 20129 Milano, Italy.
E-mail: vittorio.locatelli@unimib.it
Accepted August 1, 2001.
RC31

Cortistatin inhibits GH secretion
were collected immediately before (T=0) and 10, 20, and 30
min after drug administration.
All blood samples were immediately centrifuged, and plas-
ma was separated and stored at –20 C until processed for
GH assay.
A
Cortistatin
20
0
40 µg/kg
-20
-40
-60
-80
-100
GH assay
80 µg/kg
160 µg/kg
320 µg/kg
Plasma rat GH concentrations were determined in dupli-
cate by double antibody RIA using materials supplied by the
NHPP, NIDDK, NICHD, USDA, USA. Values are ex-
pressed in terms of rat-GH-RP-2 standard (potency 2
IU/mg) as ng/ml; intra-assay variability was 6%.
Statistical analysis
0
10
20
30
Statistical evaluation of results was performed by one-way
analysis of variance (ANOVA), followed by the Dunnett’s t-
test for the comparison of differences between multiple
groups. A p<0.05 was considered to be significant.
B
Somatostatin
20
0
40 µg/kg
RESULTS
-20
-40
-60
-80
-100
Graded doses of CST-14 significantly decreased GH se-
cretion in adult male anaesthetized rats. All four doses of
CST-14 significantly inhibited GH secretion 10 and 20 min
after treatment (Fig. 1A). The effect of CST-14 had a rapid
onset, reached its maximal activity at 10 min and persisted
until 30 min post-treatment (about 50% inhibition at time
30). Calculation of the integrated GH secretion over the
30 min period (AUC0-30min) revealed that all doses effec-
tively inhibited GH secretion (AUC0-30min: 3750 179,
2079 104, 1859 279, 1658 174 and 1340 196 for saline,
CST-14 40, 80, 160 and 320 μg/kg, respectively; p<0.05).
Graded doses of native SS-14 inhibited GH release with a
profile almost superimposable to that of CST-14 (Fig. 1B).
Again, the maximal inhibitory activity was reached 10 min
after drug administration. SS, however, inhibited GH se-
cretion more effectively than CST at 20 min, but had lost al-
most completely its activity at time 30. Calculation of the
AUC0-30min showed a nice dose-dependent inhibitory effect
of SS on GH release (AUC0-30min: 3969 154, 3002 247,
2148 248, 1523 113 and 956 72 for saline, SS-14 40, 80,
160 and 320 μg/kg, respectively; p<0.05).
80 µg/kg
160 µg/kg
320 µg/kg
0
10
20
30
Time (min)
Fig. 1 - Inhibition of GH secretion following administration of cortistatin
(panel A) and somatostatin (panel B). Data are expressed as the percent
variation vs GH values in the control group. Each point represents the
mean SE of 6 determinations. Statistics: in panel A, all doses at time 10 and
20 and the 3 higher doses at time 30 are significantly different (p<0.05)
from respective controls. In panel B, all doses at time 10 and the 3 higher
doses at time 20 are significantly lower than respective controls (p<0.05).
family. The reported capability of CST-14 to bind to re-
ceptors for natural and synthetic GHS (5-7) is an exciting
possibility to develop selective antagonists to these recep-
tors.
The GHS receptors are widely distributed within the body
(8) where they participate in the regulation of different en-
docrine and non-endocrine functions (9, 10). It will be
therefore relevant to extend the comparison between CST
and SS, and their interactions, also to the other known ac-
tivities regulated by the GHS system.
The reported inhibitory activity of CST on GH secretion
and its similarity with SS cannot exclude a different mech-
anism of action. SS has its principal site of action on its pi-
tuitary receptors and CST, in addition to the latter, might
have also acted antagonizing the “physiological” stimulato-
ry tone of endogenous GHS. In line with this hypothesis,
CST-14 and the SS analog vapreotide, but not SS-14, have
DISCUSSION
For the first time we report herein that CST-14 is active
in vivo to reduce GH secretion in normal male anaesthetized
rats. The inhibitory activity of CST is clear-cut and dose-
related. Comparison with the inhibitory effect evoked by
graded doses of native SS-14 in the same experimental con-
ditions indicates that both neuropeptides share an over-
lapping GH-reducing activity, likely mediated by an action at
the five cloned SS receptor subtypes. This finding might sug-
gest a minor physiological relevance, as CST mRNA ex-
pression is relatively low in the hypothalamus (1). However,
the known different pharmacological profile of SS and CST
opens a new attractive window in the biology of the statin
RC32

R. Deghenghi, R. Avallone, A. Torsello, et al.
5. Deghenghi R., Papotti M., Ghigo E., Muccioli G., Locatelli V.
Somatostatin octapeptides (lanreotide, octreotide, vapreotide,
and their analogs) share the growth hormone releasing pep-
tide receptor in the human pituitary gland. Endocrine 2001,
14: 29-33.
been shown to effectively displace the binding of 125I-hu-
man ghrelin, the endogenous GHS labeled for binding pur-
poses, to human pituitary and hypothalamic membranes (7),
suggesting that a SS-like agent might exist as an endogenous
ligand. This hypothesis received confirmation when it was
shown that CST, but not SS or SS-fragments, bind to the
GHS-receptor in human pituitary tissues (6). Studies in
progress in our laboratories will hopefully clarify this in-
triguing event in the forthcoming future.
6. Deghenghi R., Papotti M., Ghigo E., Muccioli G. Cortistatin,
but not somatostatin, binds to growth hormone secretagogue
receptors of human pituitary gland. J. Endocrinol. Invest. 2000,
23: 1-3.
7. Muccioli G., Papotti M., Locatelli V., Ghigo E., Deghenghi R.
Binding of 125I-labeled ghrelin to membranes from human hy-
pothalamus and pituitary gland. J. Endocrinol. Invest. 2001, 24:
RC7-RC9.
REFERENCES
1. Spier A.D., de Lecea L. Cortistatin: a member of somatostatin
neuropeptide family with distinct physiological functions. Brain
Res. Rev. 2000, 33: 228-241.
2. Siehler S., Seuwen K., Hoyer D. 125I Tyr10-cortistatin-14 labels
all five somatostatin receptors. Naunyn Schmiedebergs Arch.
Pharmacol. 1998, 357: 483-489.
8. Papotti M., Ghe C., Cassoni P., Catapano F., Deghenghi R., Ghigo
E., Muccioli G. Growth hormone secretagogue binding sites in
peripheral human tissues. J. Clin. Endocrinol. Metab. 2000, 85:
3803-3807.
9. Müller E.E., Locatelli V., Cocchi D. Neuroendocrine control
of growth hormone secretion. Physiol. Rev. 1999, 79: 511-
607.
3. Bell G.l., Reisine T. Molecular biology of somatostatin receptor.
Trends Neurosci. 1993, 16: 34-38.
10. Ghigo E., Arvat E., Giordano R., Broglio F., Gianotti L., Maccario
M., Bisi G., Graziani A., Papotti M., Muccioli G., Deghenghi R.,
Camanni F. Biologic activities of growth hormone secretagogues
in humans. Endocrine 2001, 14: 87-93.
4. de Lecea L., Criado J.R., Prospero-Garcia O., Gautvik K.M.,
Schweitzer P., Danielson P.E., Dunlop C.L., Siggins G.R., Henriksen
S.J., Sutcliffe J.G. A cortical neuropeptide with neuronal depres-
sant and sleep-modulating properties. Nature 1996, 381: 242-245.
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