NCBI Summary:
The hormone somatostatin has active 14 aa and 28 aa forms that are produced by alternate cleavage of the single preproprotein encoded by this gene. Somatostatin is expressed throughout the body and inhibits the release of numerous secondary hormones by binding to high-affinity G-protein-coupled somatostatin receptors. This hormone is an important regulator of the endocrine system through its interactions with pituitary growth hormone, thyroid stimulating hormone, and most hormones of the gastrointestinal tract. Somatostatin also affects rates of neurotransmission in the central nervous system and proliferation of both normal and tumorigenic cells. [provided by RefSeq, Jul 2008]
General function
Ligand, Hormone
Comment
Reproductive Responses to Daily Injections with Porcine Somatotropin Before Mating in Gilts. Gatford KL et al. Litter size and progeny birth weights are lower in gilts than in sows. Somatotropin (ST) is an important regulator of ovulation, fetal growth and survival. We therefore investigated effects of pST treatment of gilts for two to four weeks before mating on ovulation rate, behavioural estrus, fetal growth and survival, litter size and birth weights. In Experiment One, gilts were injected with 0, 30, 60 or 90 microg pST/kg/d for 14 days commencing 7 days after first estrus. Reproductive tracts were collected and corpora lutea and follicle numbers counted 5.5 days after second estrus. Ovulation rate (P=0.031) and number of medium-sized follicles (P=0.059) correlated positively with pST dose. In Experiment Two, gilts were injected with 0, 12.5, 25 or 50 microg pST/kg/d for 21 days from first estrus, and mated at second estrus. Numbers of corpora lutea, follicles and fetuses were counted at day 31 of pregnancy. Numbers of medium follicles and ovary weights were positively related to pST dose. In Experiment Three, 31 week old (1(st) replicate) or 27 week old (2(nd) replicate) gilts were injected daily with 0 or 12.5 microg pST/kg/d until mating 25.9 +/- 0.6 days later, and delivered at term. Pre-mating pST increased total litter size in younger gilts in the 2(nd) replicate only (P<0.05). In conclusion, injecting gilts with pST before mating does not consistently alter ovulation rate, increases the number of medium follicles available for recruitment at the second mating after treatment and increased subsequent litter size in younger gilts.
Cellular localization
Secreted
Comment
Responses of somatostatin, beta-endorphin and dynorphin A to a glucose load in two groups of women with polycystic ovarian syndrome. Wu XK et al. (1997) To investigate the relationship between elevated LH, hyperinsulinemia and neuropeptides in polycystic ovarian syndrome (PCOS), we measured the endogenous levels of insulin, somatostatin (SS), beta-endorphin (beta-EP) and dynorphin A (Dyn A) before and after a glucose load in three groups: group 1 (LH/ FSH > or = 3, n = 30); group 2 (LH/FSH < 3, n = 25), and controls (n = 15). In the basal state, significantly negative correlations were found between LH and SS (r = -0.51, p < 0.05) in group 1 and between LH and beta-EP (r = -0.49, p < 0.05) in group 2. After a glucose load, PCOS women had greater beta-EP and Dyn A responses in group 1 and impaired SS response in group 2 as compared with the control. The data suggest endogenously lower SS, higher beta-EP and Dyn A may contribute to the elevation of LH and insulin secretions in PCOS.//////////////////
Ovarian function
Initiation of primordial follicle growth, Steroid metabolism, Oogenesis, Oocyte maturation, Early embryo development
Comment
Kit Ligand and the Somatostatin Receptor Antagonist, BIM-23627, Stimulate in Vitro Resting Follicle Growth in the Neonatal Mouse Ovary. Gougeon A et al. In the mammalian ovary, kit ligand (KL), coded by a cAMP-stimulatable gene, is a protein that promotes initiation of follicle growth. The neuropeptide somatostatin (SST) is a small peptide that inhibits cAMP generation in many cell types. Consequently, SST receptor agonists might alter KL production and subsequent follicle growth. The present study was undertaken to look for the existence of a functional SST system in the mouse ovary, to test the effects of the SST receptor 2 (SSTR-2) antagonist BIM-23627 on in vitro folliculogenesis, and to compare them with those of KL, which was demonstrated to stimulate follicle growth in the neonatal rat ovary. Pairs of ovaries from 5-d-old mice were incubated in vitro during 15 d in the presence of either KL or BIM-23627. For every mouse, one ovary was cultured in culture medium (control), and the other ovary was cultured in the presence of either KL or BIM-23627. After 5, 10, and 15 d culture, the ovaries were histologically assessed for the content of primordial, primary, and secondary follicles. The SSTR-2 and -5, but not SST, were identified at the transcriptional and translational (mainly in granulosa cells) levels. Both KL and BIM-23627 triggered a reduction of the percentages of primordial follicles and an increase of the percentages of primary and secondary follicles when compared with control ovaries from the same animal. In conclusion, extraovarian SST, acting through its receptors 2 and 5 present on granulosa cells, may be involved in mouse folliculogenesis by reducing recruitment of resting follicles.
Somatostatin can alter fertility genes expression, oocytes maturation, and embryo development in cattle. Moaeen-ud-Din M et al. This study was designed to investigate the effect of somatostatin on oocytes maturation and subsequent embryo development in cattle. Bovine granulosa cells separated from oocytes, cultured for 24 h and transfected with pEGFP-N1 vector with mouse SST gene (Experimental) and with out plasmid transfection (Control). RT-PCR and Real-Time PCR were used to estimate the expression of bovine receptors of androgen, estrogen beta, growth hormone, and follicular stimulating hormone. Culture media concentrations of hormones were measured by kits using radioimmunoassay. COCs aspirated from ovaries were co-cultured with granulosa cells layers (transfected or control) at 38.5 degrees C in CO(2) incubator for maturation. We found a significant (2.37X) increase in estrogen receptor beta expression in experimental group. There was a decrease in androgen receptor, growth hormone releasing hormone receptor, and follicular stimulating hormone receptor (P < 0.05). But, 96 h of post transfection, culture media concentration of estradiol-17beta was increased significantly (P < 0.05) and testosterone, growth hormone and follicular stimulating hormone showed opposite trend (P < 0.05) in experimental groups. Co-culture of somatostatin transfected granulosa cells with oocytes, reduced the maturation rate from 70% to 66% but had no effect on subsequent fertilization and embryo development.
Andreani CL examined the effects of somatostatin on (i) androgen biosynthesis using whole rat ovarian
dispersates, and (ii) aromatase activity and progesterone production using rat granulosa cells. HCG- and insulin-stimulated accumulation of androsterone by
these cells was inhibited significantly by somatostatin. Both aromatase activity and progesterone
production stimulated by FSH and FSH plus insulin in granulosa cells were inhibited by somatostatin.
Holst N, et al. reported the regulation of insulin-like growth factor-binding protein-1 and progesterone secretion from human
granulosa-luteal cells by an agonist of somatostatin octreotide. Rajkumar K et al reported the inhibitory action of somatostatin-14 on hormone-stimulated cyclic
adenosine monophosphate induction in porcine granulosa and luteal cells.
Holst N, et al. reported that somatostatin in physiological concentrations inhibits basal and enhances luteinizing hormone-stimulated
progesterone release from human granulosa-luteal cells.
Pawelczyk LA, et al. reported that an agonist of somtostatin, Sandostatin has no direct effect on ovarian steroidogenesis in vitro.
The addition of synthetic SRIH-14 stimulated meiotic maturation in cumulus-enclosed rat oocytes, with dose
dependency being observed at SRIH-14 concentrations between 1 and 1000 pmol/l McIntyre HD et al .
Expression regulated by
Comment
van der Meer M et al that octreotide lowers ovarian sensitivity
for FSH through suppression of IGF-I/IGFBP-3 in patients with PCOS.
Ovarian localization
Granulosa
Comment
Immunoreactive SRIH was detected in the rat ovary by McIntyre HD et al and was
localized to the granulosa cells.
Gel chromatography showed peaks of
immunoreactivity co-eluting with SRIH-14, SRIH-28 and a high molecular weight component.