Effects of ghrelin and its analogues on chicken ovarian granulosa cells.
Domest Anim Endocrinol
; 34(2): 125-34, 2008 Feb.
Article
em En
| MEDLINE
| ID: mdl-17207955
ABSTRACT
The aim of these in vitro experiments was (1) to examine the effects of ghrelin on the basic functions of ovarian cells (proliferation, apoptosis, secretory activity); (2) to determine the possible involvement of the GHS-R1a receptor and PKA- and MAPK-dependent post-receptor intracellular signalling cascades; (3) to identify the active part of the 28-amino acid molecule responsible for the effects of ghrelin on ovarian cells. We compared the effect of full-length ghrelin 1-28, a synthetic activator of GHS-R1a, GHRP6, and ghrelin molecular fragments 1-18 and 1-5 on cultured chicken ovarian cells. Indices of cell apoptosis (expression of the apoptotic peptide bax and the anti-apoptotic peptide bcl-2), proliferation (expression of proliferation-associated peptide PCNA), and expression of protein kinases (PKA and MAPK) within ovarian granulosa cells were analysed by immunocytochemistry. The secretion of progesterone (P(4)), testosterone (T), estradiol (E(2)) and arginine-vasotocin (AVT) by isolated ovarian follicular fragments was evaluated by RIA/EIA. It was observed that accumulation of bax was increased by ghrelin 1-28, GHRP6 and ghrelin 1-18, but not by ghrelin 1-5. Expression of bcl-2 was suppressed by addition of ghrelin 1-28, GHRP6 and ghrelin 1-5, but promoted by ghrelin 1-18. The occurrence of PCNA was reduced by ghrelin 1-28, GHRP6, ghrelin 1-18 and ghrelin 1-5. An increase in the expression of MAPK/ERK1, 2 was observed after addition of ghrelin 1-28, GHRP6 and ghrelin 1-18, but not ghrelin 1-5. The accumulation of PKA decreased after treatment with ghrelin 1-28 and increased after treatment with GHRP6 and ghrelin 1-18 but not ghrelin 1-5. Secretion of P(4) by ovarian follicular fragments was decreased after addition of ghrelin 1-28 or ghrelin 1-5 but stimulated by GHRP6 and ghrelin 1-18. Testosterone secretion was inhibited by ghrelins 1-28 and 1-18, but not by GHRP6 or ghrelin 1-5. Estradiol secretion was reduced after treatment with ghrelin 1-28 but stimulated by ghrelins 1-18 and 1-5; GHRP6 had no effect. AVT secretion was stimulated by ghrelin 1-28, GHRP6 and ghrelin 1-18, but inhibited by ghrelin 1-5. The comparison of the effects of the four ghrelin analogues on nine parameters of ovarian cells suggest (1) a direct effect of ghrelin on basic ovarian functions-apoptosis, proliferation, steroid and peptide hormone secretion; (2) that the majority of these effects can be mediated through GHS-R1a receptors; (3) an effect of ghrelin on MAPK- and PKA-dependent intracellular mechanisms, which can potentially mediate the action of ghrelin at the post-receptor level; (4) that ghrelin residues 5-18 may be responsible for the major effects of ghrelin on the avian ovary.
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Base de dados:
MEDLINE
Assunto principal:
Grelina
/
Células da Granulosa
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article