Contractile response of isoprenaline (IC50 = 13 nM)[1]

Cyclic somatostatin (0-10 μM; 15 min) dose-dependently suppresses the rat ventricular cardiomyocytes' contractile response to isoproterenol with an IC50 value 13 nM[1].

In ruminants, visceral metabolism is impacted by cyclic somatostatin (5 μg/kg; injected intravenously every hour for 18–22 hours) [3].

Somatostatin-14 elicits negative inotropic and chronotropic actions in atrial myocardium. Less is known about the effects of somatostatin-14 in ventricular myocardium. The direct contractile effects of somatostatin-14 were assessed using ventricular cardiomyocytes isolated from the hearts of adult rats. Cells were stimulated at 0.5 Hz with CaCl2 (2 mM) under basal conditions and in the presence of the beta-adrenoceptor agonist, isoprenaline (1 nM), or the selective inhibitor of the transient outward current (Ito), 4-aminopyridine (500 microM). Somatostatin-14 did not alter basal contractile response but it did inhibit (IC50 = 13 nM) the response to isoprenaline (1 nM). In the presence of 4-aminopyridine (500 microM), somatostatin-14 stimulated a positive contractile response (EC50 = 118 fM) that was attenuated markedly by diltiazem (100 nM). These data indicate that somatostatin-14 exerts dual effects directly in rat ventricular cardiomyocytes: (1) a negative contractile effect, observed in the presence of isoprenaline (1 nM), coupled to activation of Ito; and (2) a previously unreported and very potent positive contractile effect, unmasked by 4-aminopyridine (500 microM), coupled to the influx of calcium ions via L-type calcium channels. The greater potency of somatostatin-14 for producing the positive contractile effect indicates that the peptide may exert a predominantly stimulatory influence on the resting contractility of ventricular myocardium in vivo, whereas the negative contractile effect, observed at much higher concentrations, could indicate that localized elevations in the concentration of the peptide may serve as a negative regulatory influence to limit the detrimental effects of excessive stimulation of cardiomyocyte contractility[1].

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mRNA and protein expression of each receptor subtype were quantified by RT-PCR and immunoblotting respectively; for contraction studies, cells were stimulated at 0.5 Hz under basal conditions and in the presence of isoprenaline (ISO, 10(-8)M). Results: all five SRIF (SSTR) receptor subtypes were expressed in cardiomyocytes although SRIF1A (SSTR2) and SRIF2A (SSTR1) were less abundant than the other subtypes. L803087 (10(-8)M), a SRIF2B (SSTR4) agonist, attenuated ISO-stimulated peak contractile amplitude and prolonged relaxation time (T(50)). L796778 (10(-7)M), a SRIF1C (SSTR3) agonist, augmented basal and ISO-stimulated peak contractile amplitude; L779976 (10(-8)M) and L817818 (10(-9)M), agonists at SRIF1A (SSTR2) and SRIF1B (SSTR5) receptors, respectively, also augmented ISO-stimulated peak amplitude. Conclusion: These data support involvement of SRIF2B (SSTR4) receptors in the negative contractile effects of SRIF-14, while one or more of the three SRIF1 receptor subtypes (SSTR2, 3 or 5) may contribute to the positive contractile effects of SRIF-14.[2]

Animal/Disease Models: Polypay sheep [3]
Doses: 5 μg/kg
Route of Administration: intravenous (iv) (iv)injection; 5 μg/kg once an hour; lasts for 18-22 hrs (hrs (hours))
Experimental Results: Glucose, α-amino N, ammonia N, b-hydroxybutyric acid Net portal venous excretion of splanchnic release, oxygen consumption, hepatic oxygen consumption, and total splanchnic α-amino-N release and oxygen consumption were diminished. Increases lactate release and net hepatic glucose output.

[1]. Murray F, et al. Positive and negative contractile effects of somatostatin-14 on rat ventricular cardiomyocytes. J Cardiovasc Pharmacol. 2001 Mar;37(3):324-32.
[2]. Bell D, et al. SRIF receptor subtype expression and involvement in positive and negative contractile effects of somatostatin-14 (SRIF-14) in ventricular cardiomyocytes. Cell Physiol Biochem. 2008;22(5-6):653-64.
[3]. https://pubmed.ncbi.nlm.nih.gov/9374319/

Somatostatin is a fourteen-membered heterodetic cyclic peptide comprising the sequence Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys cyclised by a disulfide bridge between the two Cys residues at positions 3 and 14. It is a heterodetic cyclic peptide and a peptide hormone.

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Somatostatin, also known as growth hormone-inhibiting hormone, is a naturally-occurring peptide hormone of 14 or 28 amino acid residues that regulates the endocrine system. It is secreted by the D cells of the islets to inhibit the release of insulin and glucagon, and is also generated in the hypothalamus, where it inhibits the release of growth hormone and thyroid-stimulating hormones from the anterior pituitary. Somatostatin is initially secreted as a 116 amino acid precursor, preprosomatostatin, which undergoes endoproteolytic cleavage to prosomastatin. Prosomastatin is further process into two active forms, somatostatin-14 (SST-14) and somatostatin-28 (SST-28), an extended SST-14 sequence to the N-terminus. The actions of somatostatin are mediated via signalling pathways of G protein-coupled somatostatin receptors. Antineoplastic effects and potential uses of somatostatin on various tumours, including pituitary adenomas, GEP-NETs, paragangliomas, carcinoids, breast cancers, malignant lymphoma and small-cell lung cancers, have been extensively investigated. Somatostatin has been used in the clinical setting for the diagnosis of acromegaly and gastrointestinal tract tumours. Its analogues have been developed to achieve more favourable kinetics for efficiency use in the management of acute conditions, such as esophageal varices. [DB00104] is a long-acting analogue of somatostatin that inhibits the release of a number of hormones, and is clinically used to relieve symptoms of uncommon gastroenteropancreatic endocrine tumours, as well as treat acromegaly.

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Recombinant Somatostatin is a recombinant peptide chemically identical or similar to endogenous somatostatin. Somatostatin is a cyclic tetradecapeptide regulating many endocrine and nervous system functions. Somatostatin inhibits release of adenohypophyseal growth hormone, thyrotropin and corticotropin, pancreatic insulin and glucagon, gastric mucosal gastrin, intestinal mucosal secretin, and renal renin by binding to specific somatostatin receptors (SSTR), which are cell surface G protein-coupled receptors expressed in a tissue-specific manner.

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A 14-amino acid peptide named for its ability to inhibit pituitary GROWTH HORMONE release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of THYROID-STIMULATING HORMONE; PROLACTIN; INSULIN; and GLUCAGON besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, SRIF-28 with a 14-amino acid extension at the N-terminal.

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Drug Indication
For the symptomatic treatment of acute bleeding from esophageal varices. Other treatment options for long-term management of the condition may be considered if necessary, once initial control has been established.

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Pharmacodynamics
Somatostatin is an endogenous peptide hormone that is secreted by the central nervous system, gastrointestinal tract, retina, peripheral neurons and pancreatic D cells of the islets of Langerhans. It exhibits several biological roles but predominantly exerts an inhibitory effect on secretion of other hormones and transmitters. While distribution of two active isoforms of somatostatin is similar, SST-14 is more predominant in the enteric neurons and peripheral nerves whereas SST-28 is more prominent in the retina and intestinal mucosal cells. **Anterior pituitary gland and brain:** It inhibits the release of growth hormones and thyroid-stimulating hormones, such as thyroid stimulating hormone (TSH) and thyrotrophin, from the anterior pituitary while inhibiting the release of dopamine from the midbrain, norepinephrine, TRH and corticotrophin-releasing hormone in the brain. **Pancreas:** In the pancreas, somatostatin reduces the secretion of glucagon and insulin as well as bicarbonate ions and other enzymes. **Thyroid gland:** Somatosatin reduces secretion of T3, T4, and calcitonin. Somatostatin regulates the thyroid function by reducing basal TSH release. **Gastrointestinal tract:** It attenuates the release of most gastrointestinal hormones such as gastrin, secretin, motilin, gastric acid, enteroglucagon, cholecystokinin (CCK), vasoactive intestinal peptide (VIP), gastric inhibitory polypeptide (GIP), intrinsic factor, pepsin, neurotensin, as well as bile secretion and colonic fluid secretion. **Adrenal gland:** It inhibits angiotensin II-stimulated aldosterone secretion and acetylcholine-induced medullary catecholamine secretion. **Eye/retina:** Somatostatin inhibits the production of vascular endothelial growth factor. **Inflammatory cells and sensory nerves:** The expression of somatostatin has been found in inflammatory cells such as lymphocytes, monocytes, macrophages and endothelial cells to act as an autocrine or paracrine regulator in local immune responses. Findings suggest that somatostatin may play a role in exerting local and systemic anti-inflammatory and antinociceptive effects. On primary afferent neurons, somatostatin reduces the responses to thermal stimulation in C-mechanoheat sensitive fibers in a dose-dependent fashion and reduces the responses of C-mechanoheat fibers to bradykinin-induced excitation and sensitization to heat. Somatostatin is reported to elicit an analgesic effect when applied intrathecally; there is evidence supporting that similar effects may occur when systemically used to treat endocrine disorders. Somatostatin is thought to reduce bleeding from esophageal varices by causing splanchnic vasoconstriction. Somatostatin elicits anti-neoplastic actions on various tumours via direct or indirect effects, or a combination of both.

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Absorption
This pharmacokinetic data is irrelevant.

Route of Elimination
As a polypeptide chain, somatostatin is primarily eliminated via metabolism by peptidase enzymes.

Clearance
Following intravenous administration of 3H-labeld endogenous somatostatin, the total body clearance was approximately 50 mL/min. In man, the value was calculated to be as high as 3000 mL/minutes, which is greatly exceeds the hepatic blood flow. This suggests that rapid enzymatic breakdown in the circulation and other tissues serves as a critical route of elimination.

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Metabolism / Metabolites
Somatostatin is rapidly degraded by peptidase enzymes present in cells and plasma.

Biological Half-Life
The half-life of endogenous somatostatin is 1-3 minutes due to rapid degradation by peptidase enzymes present in the plasma and tissues.

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Mechanism of Action
Somatostatin binds to 5 subtypes of somatostatin receptors (SSTRs), which are all Gi-protein-coupled transmembrane receptors that inhibits adenylyl cyclase upon activation. By inhibiting intracellular cyclic AMP and Ca2+ and by a receptor-linked distal effect on exocytosis, SSTRs block cell secretion. The common pathway shared by the receptors involve the activation of phosphotyrosine phosphatase (PTP), and modulation of mitogen-activated protein kinase (MAPK). With the exception of SSTR3, activation of SSTRs lead to activation of voltage-gated potassium channels accompanied by increased K+ currents. This result in membrane hyperpolarization and inhibits depolarization-induced Ca2+ influx through voltage-sensitive Ca2+ channels. Depending on the receptor subtype, signalling cascades involve activation of other downstream targets such as Na+/H+ exchanger, Rho GTPase, and nitric oxide synthase (NOS). SSTRs 1 to 4 bind both somatostatin isoforms with equal nanomolar binding affinity whereas SSTR5 exhibits a 5- to 10-fold higher binding affinity for SST-28. **Effects of SSTR1:** Upon biding of somatostatin and activation, SSTR1 mediates an antisecretory effect on growth hormone, prolactin and calcitonin. **Effects of SSTR2:** SSTR2 subtype dominates in endocrine tissues. By binding to SST2 receptors, somatostatin exerts paracrine inhibitory actions on gastrin release from G cells, histamine release from ECL cells, and directly on parietal cell acid output. SSTR2 receptor signalling cascades also inhibit the secretion of growth hormone and that of adrenocorticotropin, glucagon, insulin, and interferon-γ. **Effects of SSTR3:** Activation of these receptors lead to reduction in cell proliferation. SSTR3 triggers PTP-dependent cell apoptosis accompanied by activation of p53 and the pro-apoptotic protein Bax. A study of the matrigel sponge assay suggests that through SSTR3-mediated inhibition of both NOS and MAPK activities may lead to the antitumor effects of somatostatin in inhibiting tumor angiogenesis. **Effects of SSTR4:** The functions of SSTR4 remain largely unknown. **Effects of SSTR5:** Like SSTR2, SSTR5 subtype also predominates in endocrine tissues. Upon activation, SSTR5 signalling cascades exert an inhibitory action on growth hormone, adrenocorticotropin, insulin, and glucagon-like peptide-1 as well as the secretion of amylase. The presence of somatostatin receptors has been identified in most neuroendocrine tumours, endocrine gastroenteropancreatic (GEP) tumors, paragangliomas, pheochromocytomas, medullary thyroid carcinomas (MTC) and small cell lung carcinomas. The antitumor effects of somatostatin were also effective in various malignant lymphomas and breast tumours. Gastrointestinal hormones, such as gastrin, secretin, and cholecystokinin (CCK), as well as growth hormones and growth factors are thought to be elevated in gastrointestinal tract and neuroendocrine tumours and are inhibited by somatostatin. _In vitro_, somatostatin inhibited epidermal growth factor (EGF)-induced DNA synthesis and replication following which suggest that somatostatin may have direct anti-proliferative effects via SSTR signalling. Acromegaly is characterized as the endocrine disorder caused by a functioning tumour of cells that secrete growth hormone from the anterior pituitary. Somatostatin analogue therapies serve to normalize the elevated levels of GH and insulin-like growth factor 1 (IGF-1) and attenuate tumour growth. In the vascular system this likely produces vasoconstriction by inhibiting adenylate cyclase leading to a lowering the concentration of cyclic adenosine monophosphate in the endothelial cells which ultimately blocks vasodilation through this pathway. This vasoconstriction is though the be responsible for reducing blood flow to the esophageal tissues and so reduces bleeding from esophageal varices. Somatostatin mediates an analgesic activity by reducing vascular and nociceptive components of inflammation. Studies indicate that somatostatin may be present in nociceptive DRG neurons with C-fibers and primary afferent neurons to inhibit the release of transmitters at the presynaptic junctions of the sensory-efferent nerve terminals. Exogenous somatostatin has shown to inhibit the release of Substance P from central and peripheral nerve ending.

C78H108N18O21S2

1697.947

1696.737

54472-66-1

54472-66-1 (acetate);38916-34-6;

86278199

Typically exists as solid at room temperature

-4.25

23

26

26

119

3270

15

S1C[C@@H](C(N[C@H](C(N[C@@H](CC(N)=O)C(N[C@@H](CC2C=CC=CC=2)C(N[C@@H](CC2C=CC=CC=2)C(N[C@H](C(N[C@H](C(N[C@H](C(N[C@H](C(N[C@H](C(N[C@H](C(N[C@H](C(=O)O)CS1)=O)CO)=O)[C@@H](C)O)=O)CC1C=CC=CC=1)=O)[C@@H](C)O)=O)CCCCN)=O)CC1=CNC2C=CC=CC1=2)=O)=O)=O)=O)CCCCN)=O)NC(CNC([C@H](C)N)=O)=O.OC(C)=O

GFYNCDIZASLOMM-HMAILDBGSA-N

InChI=1S/C76H104N18O19S2.C2H4O2/c1-41(79)64(100)82-37-61(99)83-58-39-114-115-40-59(76(112)113)92-72(108)57(38-95)91-75(111)63(43(3)97)94-71(107)54(33-46-23-11-6-12-24-46)90-74(110)62(42(2)96)93-66(102)51(28-16-18-30-78)84-69(105)55(34-47-36-81-49-26-14-13-25-48(47)49)88-68(104)53(32-45-21-9-5-10-22-45)86-67(103)52(31-44-19-7-4-8-20-44)87-70(106)56(35-60(80)98)89-65(101)50(85-73(58)109)27-15-17-29-77;1-2(3)4/h4-14,19-26,36,41-43,50-59,62-63,81,95-97H,15-18,27-35,37-40,77-79H2,1-3H3,(H2,80,98)(H,82,100)(H,83,99)(H,84,105)(H,85,109)(H,86,103)(H,87,106)(H,88,104)(H,89,101)(H,90,110)(H,91,111)(H,92,108)(H,93,102)(H,94,107)(H,112,113);1H3,(H,3,4)/t41-,42+,43+,50-,51-,52-,53-,54-,55-,56-,57-,58-,59-,62-,63-;/m0./s1

Ala-gly-cys-lys-asn-phe-phe-trp-lys-thr-phe-thr-ser-cys acetate (Disulfide bond)

Somatostatin Acetate growth hormone–inhibiting hormoneGHIH

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)