Calcitonin gene-related peptide in vivo positive inotropy is attributable to regional sympatho-stimulation and is blunted in congestive heart failure

Calcitonin gene-related peptide (CGRP) is a nonadrenergic/noncholinergic (NANC) peptide with vasodilatative/inotropic action that may benefit the failing heart. However, precise mechanisms for its in vivo inotropic action remain unclear. To assess this, dogs with normal or failing (sustained tachypacing) hearts were instrumented for pressure-dimension analysis. In control hearts, CGRP (20 pmol/kg per minute) enhanced cardiac contractility (eg, +33+/-4.2% in end-systolic elastance) and lowered afterload (-14.2+/-2% in systemic resistance, both P<0.001). The inotropic response was markedly blunted by heart failure (+6.5+/-2%; P<0.001 versus control), whereas arterial dilation remained unaltered (-19.3+/-5%). CGRP-positive inotropy was not attributable to reflex activation because similar changes were observed in the presence of a ganglionic blocker. However, it was fully prevented by the beta-receptor antagonist (timolol), identifying a dominant role of sympatho-stimulatory signaling. In control hearts, myocardial interstitial norepinephrine assessed by microdialysis almost doubled in response to CGRP infusion, whereas systemic plasma levels were unchanged. In addition, CGRP receptors were not observed in ventricular myocardium but were prominent in coronary arteries and the stellate ganglia. Ventricular myocytes isolated from normal and failing hearts displayed no inotropic response to CGRP, further supporting indirect sympatho-stimulation as the primary in vivo mechanism. In contrast, the peripheral vasodilatative capacity of CGRP was similar in femoral vascular rings from normal and failing hearts in dogs. Thus, CGRP-mediated positive inotropy is load-independent but indirect and attributable to myocardial sympathetic activation rather than receptor-coupled stimulation in canine hearts. This mechanism is suppressed in heart failure, so that afterload reduction accounts for CGRP-enhanced function in this setting.     

Effects of in vivo stimulation on molecular forms of circulatory calcitonin and calcitonin gene-related peptide in man

Multiple molecular weight forms of the potent vasodilator peptide calcitonin gene-related peptide (CGRP) are present in the circulation in man. The monomeric form of CGRP(1-37) and CT(1-32) account for only a fraction of the total immunoreactive CGRP and calcitonin (CT) in the circulation. In vivo release of various molecular weight forms of CGRP and CT, including the monomeric form, into the circulation was demonstrated by gel-permeation chromatography, following stimulation of the gastrointestinal tract by a meal, and C-cells of the thyroid gland with pentagastrin. Following these stimulations an increase of the levels of C-terminal fragment of CGRP was also observed indicating a rapid metabolic breakdown of CGRP in vivo. In addition to a number of endogenous peptides and other substances, acute release of monomeric CGRP into the circulation may also contribute to the vasodilation observed following ingestion of food and administration of pentagastrin in man.     

Serotonin,calcitonin and calcitonin gene-related peptide in acute pancreatitis

Objective: The aim of this study was to investigate plasma levels of serotonin, calcitonin and calcitonin gene-related peptide (CGRP) in the course of acute pancreatitis (AP) taking organ failure, etiology and severity into consideration.

Material and methods: Sixty consecutive patients with alcohol- or gallstone-induced AP were included over a 15-month period. Patients were treated according to a standardized algorithm and monitored for organ specific morbidity and mortality. Organ functions and blood samples were assessed on days 0, 1, 2 and 14 after hospital admission. Twenty healthy volunteers, matched for age and gender, comprised the reference group.

Results: Lower levels of serotonin were observed in patients at admission compared to healthy volunteers (p?=?.021). Serotonin levels increased from day 2 to 14 (p?<?.001), but with no relation to severity, etiology or organ failure. No difference in calcitonin levels was found in patients at admission compared to healthy volunteers. However, calcitonin levels decreased over time (p?<?.001) and higher levels were found in patients with respiratory failure (p?=?.039). No difference was observed in relation to severity or etiology. CGRP levels in patients at admission did not differ from healthy volunteers, nor did CGRP change over time or show any relationship to severity, etiology or organ failure.

Conclusion: Our data suggest serotonin and calcitonin levels to be associated to time-course of AP, and calcitonin levels to organ dysfunction. We hypothesize that serotonin plays a pathogenic role in the compromised pancreatic microcirculation, and calcitonin a role as a biomarker of severity in AP.     

Stabilization of cardiac rhythm in subsequently fatal ventricular tachycardia and fibrillation by calcitonin gene-related peptide.

A potentially fatal arrhythmia was encountered in a patient with a previous myocardial infarction, who was resistant to treatment with lidocaine, amiodarone and electric defibrillation. Calcitonin gene-related peptide stabilized ventricular fibrillation and flutter, but the patient subsequently died.     

Colocalization of calcitonin gene-related peptide and somatostatin in pancreatic islet cells and inhibition of insulin secretion by calcitonin gene-related peptide in the rat

Calcitonin gene-related peptide (CGRP)- and somatostatin (SRIF)-containing cells were identified by immunocytochemical techniques in pancreatic islet cells of the rat. CGRP-containing cells were found primarily in the peripheral portion of the pancreatic islets. In addition, CGRP-containing cells also contained somatostatin, which identifies the islet CGRP-containing cells as D cells. In the present study, we also tested the effect of CGRP on gastrin-releasing peptide (GRP; 10(-9) M)- or cholecystokinin (CCK-8, 10(-9) M)-stimulated release of insulin from isolated rat islets in vitro. At concentrations of 10(-8)-10(-11) M, CGRP inhibited GRP- and CCK-8-stimulated release of insulin significantly when compared with GRP or CCK-8 alone. At the lowest concentration of CGRP (10(-11) M), the inhibitory effect of CGRP on CCK-8-stimulated release of insulin was statistically significant (p less than 0.05) and exceptionally potent (65-90% inhibition). We have also found that CGRP does not stimulate the release of SRIF from isolated islet cells. These findings suggest that CGRP may play a regulatory role in the release of insulin.     

The role of calcitonin gene-related peptide in the regulation of anion secretion by the rat and human epididymis.

A study was carried out to investigate the role of the calcitonin gene-related peptide (CGRP) in the regulation of electrolyte transport in the rat and human epididymis. In monolayer cultures derived from the rat cauda epididymal cells, CGRP stimulated the short-circuit current (SCC) in a dose-dependent manner with the EC50 (concentration required to produce 50% of the response) at 15 nmol/l. This effect of CGRP was seen when the peptide was added to the basolateral aspect of the cells; apical addition having negligible effect. The CGRP-induced rise in the SCC was dependent on the presence of chloride in the bathing solution. Calcitonin had no effect on the SCC and did not affect the CGRP-induced rise in the SCC. The effect of CGRP on secretion was inhibited in a competitive fashion by the CGRP receptor antagonist CGRP(8-37). In contrast to bradykinin, angiotensin II and endothelin I, the effect of CGRP was independent of prostaglandin synthesis. Measurement of intracellular adenosine 3':5'-cyclic monophosphate showed a time- and dose-dependent increase upon stimulation with CGRP. CGRP also stimulated the SCC in monolayers grown from the human epididymis. The current could be inhibited by apical application of the chloride channel blocker, diphenylamine-2-carboxylate. Immunoreactive CGRP was found in the epithelia of rat and human cauda epididymidis. It is suggested that CGRP may regulate the electrolyte and fluid secretion in the epididymis, thereby providing an optimal microenvironment for the maturation and storage of spermatozoa.     

Role of calcitonin gene-related peptide in hypertension-induced renal damage

Calcitonin gene-related peptide, a potent vasodilator neuropeptide, is localized in perivascular sensory nerves. We have reported that alpha-calcitonin gene-related peptide knockout mice have elevated baseline blood pressure and enhanced hypertension-induced renal damage compared with wild-type controls. Thus, the aim of this study was to determine the mechanism and functional significance of this increased hypertension-induced renal damage. We previously demonstrated by telemetric recording that the deoxycorticosterone-salt protocol produces a 35% increase in mean arterial pressure in both alpha-calcitonin gene-related peptide knockout and wild-type mice. Both strains of mice were studied at 0, 14, and 21 days after deoxycorticosterone-salt hypertension. Renal sections from hypertensive wild-type mice showed no pathological changes at any time point studied. However, on days 14 and 21, hypertensive knockout mice displayed progressive increases in glomerular proliferation, crescent formation, and tubular protein casts, as well as the inflammatory markers intercellular adhesion molecule-1, vascular adhesion molecule-1, and monocyte chemoattractant protein-1. There was a significant increase in 24-hour urinary isoprostane, a marker of oxidative stress-induced lipid peroxidation, levels at days 14 and 21 in the hypertensive knockout compared with hypertensive wild-type mice. Urinary microalbumin was significantly higher (2-fold) at day 21 and creatinine clearance was significantly decreased 4-fold in the hypertensive knockout compared with hypertensive wild-type mice. Therefore, in the absence of alpha-calcitonin gene-related peptide, deoxycorticosterone-salt hypertension induces enhanced oxidative stress, inflammation, and renal histopathologic damage, resulting in reduced renal function. Thus, sensory nerves, via alpha-calcitonin gene-related peptide, appear to be renoprotective against hypertension-induced damage.     

肠易激综合征血清中降钙素基因相关肽的变化

目的探讨降钙素基因相关肽(CGRP)在肠易激综合征(IBS)中的变化,为进一步探讨其在IBS中的作用提供证据。方法 SPF级大鼠30只,随机分为3组:模型组大鼠以0.85 mL含三硝基苯磺酸(TNBS)的50%乙醇灌肠1次诱发远端结肠炎,对照组仅以等体积的生理盐水灌肠,正常组不作处理。正常饲养30 d后处死。造模前后均以腹部回撤反射(AWR)测定内脏感觉阈值用以评价模型。造模成功后行心脏取血,以ELISA试剂盒测定血清中CGRP浓度。结果 TNBS灌肠法复制模型成功,腹部回撤反射内脏感觉阈值测定模型组造模后内脏感觉阈值较造模前及正常组下降(P<0.05)。模型组血中CGRP浓度较对照组及正常组明显升高(P<0.05),对照组较正常组中CGRP浓度也有升高但差异无统计学意义(P>0.05)。结论模型组血清中CGRP浓度升高,可能在IBS的发生中起着一定作用。     

Hypotension- and endotoxin-induced alterations in calcitonin gene-related peptide: modulation by dexamethasone

Plasma levels of calcitonin gene-related peptide (CGRP) were studied in anesthetized rats during and after recovery from hemorrhagic hypotension as well as following administration of bacterial endotoxin. Hypotension of 35-40 mmHg maintained for 2 hr resulted in significant (P less than .05) elevation of plasma CGRP levels. Plasma levels at 120 min of hypotension were 49.5 +/- 5.9 pg/ml, over 4-fold above average control levels (11.1 +/- 1.1 pg/ml). Plasma CGRP levels at 90 min of hypotension (20.2 +/- 2.4 pg/ml) or before were not more than 2.5-fold above control levels. Ninety minutes after the return of shed blood in the 30 min group, blood pressure (83 +/- 3 mmHg) and CGRP (17.2 +/- 2.2 pg/ml) were not different from saline controls (88 +/- 3 mmHg and 15.1 +/- 1.7 pg/ml CGRP). However, if hypotension was maintained for 120 min before the return of shed blood, blood pressure following 90 min recovery was significantly lower (59 +/- 5 mmHg) and CGRP levels significantly higher (39.2 +/- 5.6 pg/ml) than saline control values (82 +/- 5 mmHg and 19.5 +/- 2.7 pg/ml). Dexamethasone treatment of the 120 min hypotension group when shed blood was returned resulted in CGRP values not different from saline treated, but hypotension persisted. Administration of bacterial endotoxin (16.7 mg/kg) to anesthetized rats caused significant elevations (P less than .05 vs. saline treatment at 3 hr) in plasma CGRP levels from aorta (82.2 +/- 5.0 pg/ml), vena cava (79.4 +/- 12.9), and portal vein (117.7 +/- 29 pg/ml) compared to levels in saline-treated control rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of calcitonin and calcitonin gene-related peptide on pancreatic functions in man.

Calcitonin gene-related peptide (CGRP) has recently been identified in central and peripheral nerve fibres, including those of blood vessels supplying the exocrine pancreas, and in pancreatic islet cells. Moreover, receptors have been characterised in the same tissue. The present study examined the effects of human CGRP and of calcitonin on exocrine pancreatic secretion and on islet cell function in nine healthy volunteers. CGRP (300 ng/kg/h) caused, respectively, a 25% and 31% inhibition of caerulein stimulated trypsin and amylase output which was similar to that seen with calcitonin (300 ng/kg/h). Arginine stimulated insulin and glucagon release was unaffected by either CGRP, or calcitonin. Calcitonin gene-related peptide caused cutaneous flushing, but did not affect the pulse rate or arterial blood pressure in the doses tested. Calcitonin gene-related peptide inhibits exocrine pancreatic secretion in vivo in man, but does not affect islet cell hormone release.     

Regional differences of adenylate cyclase stimulation by calcitonin and calcitonin gene-related peptide in the human kidney

Calcitonin (CT) gene-related peptide (CGRP)-like immunoreactivity was detected in both the cortex and medullo-papillary portion of human kidneys. The two forms of human CGRP as well as rat CGRP were capable of stimulating renal cortical adenylate cyclase activity in a concentration-related manner, with a half-maximally effective concentration (EC50) similar to that of human CT and approximately 100-1000 times higher than that of salmon CT. However, in the medullo-papillary portion, in which both salmon CT and human CT were inactive, the two forms of human and rat CGRP increased adenylate cyclase activity by 100%, with EC50 values ranging from 36 nmol/L to 1 mumol/L. In cortical membrane preparations the effect of CGRP was additive to that of salmon CT. We concluded that regional differences exist in the effect of CT and CGRP in human renal tissue and that in the medullo-papillary portion and possibly in the cortex, CGRP stimulates adenylate cyclase activity through a CT-independent mechanism.     

CGRP在大鼠胃痛觉过敏形成机制中的作用

目的:探索降钙素基因相关肽(CGRP)相关的干预措施对胃痛觉过敏的影响,了解CGRP在胃痛觉过敏形成过程中发挥的作用．方法:成年SD古大鼠,均植入胃内气囊．观察伤害性扩张或CGRP iv对大鼠疼痛阈值的影响:观察由上述措施诱发内脏过敏的大鼠在给予CGRP受体特异性拮抗剂hCGRP8-37后疼痛阈值的变化:观察不同剂量CGRP和hCGRP8-37对疼痛阈值的影响．结果:CGRP iv后胃疼痛阈值为11．7±2．6 mmHg,对照组疼痛阈值为19．2±2．0 mmHg,生理盐水对照组则为18．3±2．5 mmHg,实验组与其他两组比较尸均<0．05．CGRP使大鼠的疼痛阈值降低．hCGRP8-37能逆转伤害性扩张和CGRP引起的内脏敏感性增高,该作用呈剂量依赖性(r=0．821,P<0．01)．结论:胃扩张刺激能引起胃敏感性增高,在此过程中CGRP具有重要的作用．     

Identification of calcitonin and calcitonin gene-related peptide messenger ribonucleic acid in medullary thyroid carcinomas by hybridization histochemistry

Synthesis and secretion of calcitonin and calcitonin gene-related peptide (CGRP) were studied in medullary thyroid carcinomas (MTC) by hybridization histochemistry on tissue sections and by Northern gel analysis of mRNA. Five patients with MTC and elevated serum levels of calcitonin and CGRP were studied. Surgically obtained tumor samples (four primary and three lymph node metastases) were extracted after freezing, and the RNA was fractionated on Northern gels. Hybridization was carried out with 32P-labeled synthetic oligodeoxyribonucleotides coding specifically for calcitonin and CGRP. Calcitonin- and CGRP-specific mRNAs approximately 1000 nucleotides in length were demonstrated in all 7 tumor samples. However, neither calcitonin nor CGRP mRNA was detected in a pheochromocytoma from 1 of the patients who had multiple endocrine neoplasia type II. A series of unselected lung carcinomas yielded the same result. Hybridization histochemistry was carried out on sections from the same tumors using the same probes. The mRNAs for calcitonin and CGRP were located in all cells of neoplastic MTC appearance, with CGRP mRNA at significantly lower levels. This demonstrated that both calcitonin and CGRP mRNA were present within the same tumor cells. The lung tumors and pheochromocytoma were negative with both probes. Hybridization histochemistry is likely to be of use in diagnosis of medullary thyroid cancer and in studying the calcitonin-CGRP mRNA processing mechanism in whole cells.     

Increased circulating calcitonin gene-related peptide (CGRP) in cirrhosis

The etiology of the hyperkinetic circulatory state in cirrhosis is equivocal and reduced peripheral vascular resistance is a major unsolved problem in hepatic pathophysiology. It is therefore sensible to search for vasodilators. A recently discovered neuropeptide, calcitonin gene-related peptide (CGRP), is a highly potent vasodilator. We determined the circulating concentration of immunoreactive CGRP in different vascular beds in 35 patients with cirrhosis and in eight patients with minor disorders. Plasma CGRP was significantly increased in the cirrhotic patients compared with patients with minor disorders (59 vs. 46 pmol/l, p less than 0.01), as well as with 232 healthy persons (37 pmol/l, p less than 0.0001). Moreover, circulating CGRP increased significantly with the severity of cirrhosis (Child-Turcotte group A, 56; group B, 59; group C, 71 pmol/l; p less than 0.025). No significant arterio-venous net extraction or release of CGRP was found across the hepato-intestinal system, kidney, lung or limb. In conclusion, elevated circulating CGRP may play a role in the haemodynamic derangement of cirrhosis. The lack of organ arterio-venous differences suggests a widespread release and degradation of CGRP in many tissues and gives no evidence of decreased degradation as the cause of increased plasma CGRP in patients with cirrhosis.     

Expression of calcitonin gene-related peptide in medullary thyroid cancer.

We studied the expression of calcitonin (CT) and calcitonin gene-related peptide (CGRP) in 18 patients with medullary thyroid cancer (MTC) in the neoplastic (primary or metastatic) tissue by immunohistochemistry and in the plasma by radioimmunoassay. CT immunoreactivity was found in 100% of the primary and metastatic MTC, CGRP was expressed in 66% of the primary tumors and in 73% of the metastases. Both the number of positive cells and the degree of staining were always higher for CT than for CGRP staining. While plasma CT concentrations were always increased in patients with metastases, 3 patients with metastases had undetectable plasma CGRP levels. A positive correlation was found between plasma CT and CGRP levels. These data indicate that CGRP is frequently expressed in MTC sections and that plasma CGRP measurement is an additional marker for MTC, although has no advantage with respect to CT measurements in monitoring the progression of the disease.     

The origin of circulating calcitonin gene-related peptide in the rat

It is known that in addition to the calcitonin precursor the calcitonin gene also encodes a novel peptide, calcitonin gene-related peptide (CGRP). This potent vasodilator has been found in the circulation of man. This present study demonstrates that CGRP is also found in the circulation of the rat and that plasma CGRP comes from two different sources: the thyroid, a major source in old rats, and the perivascular nerves probably at all ages.     

Cardiovascular effects of central calcitonin gene-related peptide in conscious rats

Calcitonin gene-related peptide (CGRP) is a potent peripheral vasodilator. In the present study, the cardiovascular effects of centrally administered CGRP were examined in conscious, normotensive rats. The rats were chronically instrumented with miniaturized pulsed Doppler flow probes to allow measurement of regional blood flow in the conscious animals. Injection of increasing doses of CGRP (0.3 to 3.0 micrograms/kg) in the lateral cerebroventricles transiently increased arterial pressure (maximal change = 13 +/- 3 mm Hg) and markedly increased heart rate (maximal increase = 88 +/- 10 b/min). The heart rate response was sustained over a period of 20 to 30 minutes. Central CGRP decreased hindquarter vascular resistance but had no effect on renal or mesenteric vascular resistances. In contrast, intravenous injections of CGRP reduced arterial pressure and renal, mesenteric, and hindquarter vascular resistances. The tachycardia response to central CGRP was attenuated by pretreatment with propranolol or hexamethonium, indicating that the heart rate response was mediated, in part, through increases in cardiac sympathetic tone. These data indicate that central CGRP may alter cardiovascular function through alterations in sympathetic outflow.     

Pharmacokinetics and organ-specific metabolism of calcitonin gene-related peptide in sheep

Calcitonin gene-related peptide (CGRP) is a product of the calcitonin gene with a widespread distribution in neural tissue of the brain, gut and perivascular nerves. Infusion of CGRP produces multiple biological effects, but the physiological significance of these findings will be influenced by the sites and rates of CGRP metabolism. The metabolic clearance rate and half-life of disappearance of human CGRP were estimated in conscious sheep after infusing CGRP at 1 or 5 pmol/kg per min to steady-state conditions. The particular organs involved in the clearance of CGRP were assessed by measuring the inflow and outflow concentrations across the liver, gut, kidney, lung and brain. The metabolic clearance rate at steady state was 22.6 +/- 2.1 (S.E.M.) and 15.0 +/- 17 ml/kg per min for the 1 and 5 pmol/kg per min doses respectively. The half-life of disappearance was bi-exponential: 3.6 +/- 0.3 min for the first phase and 13.6 +/- 1.0 min for the second phase. High-pressure liquid chromatography of plasma at equilibrium revealed only a single peak coeluting with CGRP(1-37): no immunoreactive metabolites were detected. These pharmacokinetic values are intermediate between that of a neurotransmitter and a hormone and are therefore consistent for a peptide with both circulatory and neurotransmitter modes of action. The kidney, with an arterial-renal vein gradient of 14%, and the liver, with a portal-hepatic vein gradient of 25%, were the major organs involved in the clearance of CGRP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Localization of calcitonin gene-related peptide in human esophageal Langerhans cells

Previously undescribed calcitonin gene-related peptide-immunoreactive intraepithelial cells were seen in specimens of esophageal mucosa obtained by biopsy or surgical resection from 14 individuals. These calcitonin gene-related peptide-immunoreactive cells were sparsely seen in normal mucosa but increased markedly in esophagitis. They were inaccessible to routine histological stains, but osmication showed them as dendritic forms resembling Langerhans cells of the skin. Their cytological identity was determined with immunocytochemical tests for human antigenic markers such as Ia, HLA-DR, and OKT6 for Langerhans cells, Leu-M5 and Leu-M3 for intraepithelial macrophages, CD3 and TCR-1 for T-lymphocytes, Leu-14 for B-lymphocytes, S-100 for Merkel cells, and chromogranin for amine precursor uptake and decarboxylation cells. Double localization showed that calcitonin gene-related peptide immunoreactivity colocalized with Ia, HLA-DR, and OKT6 but not with the other markers. These studies show that intraepithelial Langerhans cells in the esophageal mucosa contain calcitonin gene-related peptide, which may serve as an immunomodulator.     

降钙素基因相关肽对血管升压素缩血管效应的影响

目的 :探讨降钙素基因相关肽 （CGRP）对血管升压素 （AVP）缩血管效应的影响。方法 :培养大鼠主动脉血管平滑肌细胞 （VSMC） ,给予 AVP和 CGRP干预 ,检测 VSMC的细胞内游离钙离子浓度 （[Ca2 + ] i）。结果 :AVP增加VSMC的 [Ca2 + ] i,而 CGRP明显抑制 AVP的这一作用。结论 :CGRP可能通过抑制 VSMC的 [Ca2 + ] i的升高而发挥其对 AVP所致缩血管效应的抑制作用