Hormonal control of gubernaculum development during testis descent: gubernaculum outgrowth in vitro requires both insulin-like factor and androgen

The gubernaculum connects the gonad to the inguinoscrotal region and is involved in testis descent. It rapidly develops in the male fetus, whereas development in the female fetus is lacking. Possible factors involved in gubernaculum development are androgens, anti-Müllerian hormone (AMH), and insulin-like factor (Insl3). Sexual dimorphism in gubernaculum development correlated with the mitotic activity of cells in the gubernacular bulbs from male and female fetuses. Androgen receptor expression was restricted to the mesenchymal core of the gubernacular bulb, whereas skeletal muscle was detected in its outer layer. In an organ culture system devised to further study gubernaculum development in vitro, morphology of gubernacular explants grown in the presence of testes was comparable with that of gubernacula developed in vivo. Testicular tissue or medium containing R1881, a synthetic androgen, had a growth stimulatory effect on gubernacular explants compared with ovarian tissue or basal medium only. Moreover, Amh-/-, Amh+/-, and Insl3+/- testes stimulated the growth of gubernacular explants to the same extent as control testes. Insl3-/- testes, however, did not produce such an activity. This study reveals an essential role for both androgen and Insl3 in the gubernaculum outgrowth during transabdominal testis descent.     

Influence of calcitonin gene-related peptide release on pH-induced mechanical depression in rat atria.

Rat atria is richly innervated by sensory nerve fibers that release CGRP when stimulated either by capsaicin or acid pH. We studied the physiological relevance of acid pH-induced CGRP release on changes in atrial contractility and relaxation produced by lowering the pH. Isolated atria electrically paced at 2.77 Hz were exposed to a 10-minute period of metabolic acidosis (pH=6.73+/-0.01, n=28) after: 1) CGRP release induced by capsaicin 0.5 microM; 2) blockage of CGRP release with ruthenium red (RR) 5 microM; 3) no pretreatment; and 4) CGRP receptor blockage with CGRP(8-37) 1 microM. Contractility and relaxation were significantly less depressed by acid pH when CGRP release was prevented by RR or CGRP receptor activation was blocked by CGRP(8-37). The results suggest that CGRP release and the activation of CGRP receptors may be physiologically involved in contributing to the depression of contractility and relaxation induced by acid pH in rat atria.     

Specific induction of cAMP in Langerhans cells by calcitonin gene-related peptide: relevance to functional effects.

Epidermal Langerhans cells (LC) are associated anatomically with epidermal nerves, and a product of these nerves, calcitonin gene-related peptide (CGRP), inhibits the antigen-presenting capacity of LC and macrophages. As the CGRP receptor appears to be coupled to Gs alpha protein, which in turn activates adenylate cyclase, the ability of CGRP to induce cAMP in LC was examined and correlated with functional effects. LC were isolated from murine epidermal cells using antibodies on magnetic microspheres. Exposure to CGRP induced a significant increase in cAMP content, which could be inhibited by coculture with a truncated form of CGRP [CGRP-(8-37)] that is a specific competitive inhibitor of CGRP. Substance P and calcitonin failed to induce cAMP in LC. Although culture in CGRP reduced the ability of murine epidermal cells enriched for LC content to present pigeon cytochrome c to a responsive clone or to present antigen for elicitation of delayed-type hypersensitivity in immune mice, culture in forskolin had little or no effect on antigen presentation despite increased cAMP content of LC as much or more than that induced by CGRP. The effect of CGRP on antigen presentation in these systems could be blocked with CGRP-(8-37). CGRP inhibited the induction of B7-2 by lipopolysaccharide on peritoneal macrophages and a LC line, whereas calcitonin did not. CGRP induces specific accumulation of cAMP in LC and inhibits LC antigen-presenting function by a receptor-mediated event. However, the induction of cAMP by itself does not account for inhibition of antigen presentation. Suppression of the expression of B7-2 may be one mechanism by which CGRP inhibits antigen presentation.     

Amylin,released from the gastric fundus,stimulates somatostatin and thus inhibits histamine and acid secretion in mice

BACKGROUND & AIMS: Amylin, a peptide that displays 50% homology with calcitonin gene-related peptide (CGRP), is colocalized with somatostatin in endocrine cells of the gastric fundus. The present study was designed to determine the mechanism of action of amylin on gastric exocrine and endocrine secretion. METHODS: Acid secretion was measured in the isolated mouse stomach by titration. Somatostatin and histamine secretion were measured in rat fundic segments by radioimmunoassay. RESULTS: In isolated mouse stomach, amylin caused a concentration-dependent decrease in acid secretion. In rat fundic segments, amylin and CGRP each caused a concentration-dependent increase in somatostatin and a decrease in histamine secretion. Changes in histamine secretion induced by amylin reflected changes in somatostatin secretion and could be abolished by addition of somatostatin antibody. Both the somatostatin and the histamine responses to amylin were abolished by the selective amylin antagonist AC187 but were unaffected by the CGRP antagonist CGRP8-37. In contrast, the responses to CGRP were abolished by CGRP8-37 but were unaffected by AC187. AC187 alone decreased somatostatin and increased histamine in fundic segments and increased acid secretion in isolated stomach, indicating that endogenous amylin participates in the regulation of gastric endocrine (somatostatin and histamine) and exocrine (acid) secretion. CONCLUSIONS: In gastric fundus, release of amylin from somatostatin cells interacts with distinct amylin receptors to enhance somatostatin secretion via an autocrine pathway that leads to inhibition of histamine and acid secretion.     

Effect of CGRP antagonist,alpha-CGRP 8-37, on acid secretion in the dog

The recently synthesized calcitonin gene-related peptide (CGRP) antagonist, human alpha-CGRP 8-37, was used to study its effects on gastric acid secretion. Four dogs with gastric fistula were used to measure the antagonist's physiologic effects in the stomach. All dogs received a bactopeptone dextrose meal (intragastric titration to pH 5.5) with either continuous CGRP 8-37 (1000 pmol/kg/hr) or saline (control). Additionally, intravenous bombesin (75–600 ng/kg/hr) and bethanecol (12.5–100 µg/kg/hr) was tested in the presence of the antagonist. Plasma gastrin levels also were measured via radioimmunoassay (RIA) in control and CGRP 8-37-stimulated animals. Gastric acid secretion increased by 100% with infusion of 1000 pmol/kg/hr CGRP 8-37 when compared to the control. Acid output increased 98% with both intravenous antagonist and 600 ng/kg/hr bombesin when compared to bombesin alone. However, no augmentation of acid secretion by CGRP 8-37 was shown with 25 µg/kg/hr bethanecol. RIA of plasma gastrin demonstrated no effect with the antagonist when given alone and did not increase bombesin-stimulated gastrin release. We conclude that CGRP 8-37 blocks native CGRP inhibitory effects on gastric acid secretion. Our findings of potentiation of acid secretion by bombesin as well as no change in gastrin levels in the presence of the antagonist is likely due to a blockage in a noncholinergic neuron to the somatostatin cell. Furthermore, CGRP 8-37 did not increase bethanecolstimulated acid secretion, most likely due to bethanecol's (acetylcholine) nearly ubiquitous positive effects on acid secretion.Funded by NIH Grant DK 40790.     

Calcitonin gene-related peptide: effect on contractile activity and luminal cross-sectional area in the isolated, perfused porcine ileum.

Because calcitonin gene-related peptide (CGRP) is an abundant peptide in the enteric nervous system we studied the effect of intra-arterial infusions of synthetic human CGRP I in concentrations from 10(-10) to 10(-8) mol/l on contractile activity and luminal cross-sectional area in the isolated perfused porcine ileum, using manometry and impedance planimetry. The frequency of the basal contractile activity was 0.37 +/- 0.1 contractions per minute. CGRP induced phasic contractions, which at the highest dose were superimposed on tonic contractions, as determined by measurement of luminal cross-sectional area. The frequency of contractions dose-dependently increased to approximately 10/min at 10(-8) mol/l CGRP. The amplitude of contractions increased from a maximum of 35 cm H2O to 51 +/- 3 at 5 x 10(-9) mol/l CGRP and 52 +/- 6 cm H2O at 10(-8) mol/l CGRP. After the termination of CGRP infusion at the highest dose a short phase of up to 5 min with strong tonic contraction was observed. No phasic activity was detected by manometry during this phase. In conclusion, CGRP dose-dependently increased contractile activity in the pig ileum. CGRP may therefore participate in the regulation of small-intestinal motility in the pig.     

Identification and characterization of calcitonin gene-related peptide receptors in porcine renal medullary membranes.

Membranes prepared from the medullary region of the porcine kidney displayed high affinity, high density (Kd, 0.12 nM; binding capacity, 127 fmol/mg protein) receptors for calcitonin gene-related peptide (CGRP). Human CGRP (hCGRP), rat CGRP (rCGRP), and the hCGRP analog [hCGRP-(8-37)] competed for the binding of [125I]hCGRP, whereas salmon calcitonin (sCT) and CGRP-(22-37) were very weak in displacing [125I]hCGRP binding. In accordance with these binding data, CGRP stimulated adenylate cyclase activity in these membrane preparations in a concentration-dependent manner, with an EC50 similar to that of the Kd for binding. In the same preparations, sCT was ineffective in stimulating adenylate cyclase activity, suggesting that porcine kidney medullary membranes possess receptors specific for CGRP. Further hCGRP-(8-37), a CGRP antagonist, inhibited CGRP-stimulated adenylate cyclase activity in a competitive manner. Covalent cross-linking of [125I]hCGRP to these membranes resulted in the specific labeling of one major band at approximately 30,000 mol wt and two minor bands at about 58,000 and 78,000 mol wt. The presence of CGRP receptors and their coupling to adenylate cyclase suggest a role for CGRP in kidney function, such as local regulation of the microcirculation, electrolyte transport, or water homeostasis in the porcine kidney.     

Sympathetic innervation improves the contractile performance of neonatal cardiac ventricular myocytes in culture

We propose that sympathetic innervation could contribute to the improvement in cardiac contractility that normally occurs during neonatal life because these processes are developmentally coincident. Effects of sympathetic innervation were studied in primary cultures of isolated, not previously innervated ventricular cardiomyocytes from neonatal rats. Innervation was produced by addition of autologous neurons from the thoracolumbar sympathetic ganglia, and amplitude and frequency of myocyte contraction were measured by on-line video motion analysis. Sympathetic innervation significantly (P less than 0.0001) increased amplitude of contraction (by 34 +/- 8%) and decreased contraction frequency (by 36 +/- 3%). The effect of innervation on myocyte contractility was not attenuated by adrenoceptor blockade (10(-6) M propranolol and 10(-6) M phentolamine), but could be reproduced using medium conditioned by cocultures of neurons and myocytes. Sympathetic innervation improves the contractility of isolated cardiomyocytes, indicating that autonomic innervation contributes to maturation of cardiac function.     

大鼠幽门区降钙素基因相关肽与胆汁返流的关系

目的探讨降钙素基因相关肽（CGRP）及其拮抗剂（h-CGRP8—37）对正常和应激情况下大鼠胃内胆汁反流的影响。方法SD大鼠65只，实验分三部分：第一部分大鼠20只随机分为四组：对照组、CGRP低、中和高剂量组各5只，分别腹腔注射生理盐水（1ml）和CGRP（10μg／kg 1ml）、CGRP（30μg／kg 1ml）和CGRP（30μg／kg1ml），0．5h后处死，取胃液测胆汁酸（TBA）浓度。第二部分大鼠30只随机分为二组：应激组和h-CGRP8—37组各15只。从浸入水中开始取2、4、6h共3个时段，每个时段各5只。取胃液测TBA浓度。第三部分大鼠15只，分为对照组、应激即刻组（从应激开始，4小时应激结束）和应激后2h组各5只，测胃液TBA浓度，并用免疫组化SP法检测胃幽门区CGRP神经元阳性反应产物（CGRP—ir）的平均光密度变化。结果正常大鼠在腹腔注射不同剂量CGRP0．5h后胃内胆汁酸浓度明显增高；经幽门局部给予CGRP拮抗剂能显著降低应激性溃疡大鼠在2、4、6h三个时段的胃内胆汁返流；免疫组化显示应激性溃疡大鼠胆汁返流增加时，胃幽门区CGRP免疫反应阳性物质活性降低。结论CGRP能促进胃内胆汁酸反流，CGRP参与了幽门括约肌舒张功能的调控。     

Homologous desensitization of the insulinotropic glucagon-like peptide-I (7-37) receptor on insulinoma (HIT-T15) cells.

Glucagon-like peptide-I(7-37) [GLP-I(7-37)] is an intestinal peptide with potent insulinotropic activities on pancreatic beta-cells in vivo and in vitro. In earlier studies elevated concentrations GLP-I(7-37) inhibited insulin release and cAMP generation in beta-cells. We now show that the GLP-I(7-37) receptor in the glucose-responsive B-cell line HIT-T15 undergoes rapid and reversible homologous desensitization in response to supraphysiological concentrations of GLP-I(7-37). GLP-I(7-37) stimulated insulin release and cAMP generation in a glucose-dependent biphasic manner with a maximum stimulation at 10 nmol/liter. The first-phase insulin secretory response was reduced by 41% at doses of GLP-I(7-37) of 100 nmol/liter and higher. Preperifusion of B-cells with 100 nmol/liter GLP-I(7-37) for 5 or 10 min reduced a subsequent insulin secretory response to 10 nmol/liter GLP-I(7-37) after hormone washout and recovery periods of 10 min (52% and 55% reduction) or 30 min (33% reduction or full recovery). Preperifusion of HIT-T15 cells with 100 nmol/liter glucagon (10 min) or 100 nmol/liter gastric inhibitory peptide (GIP) (10 min) had no effect on the insulin secretory response to 10 nmol/liter GLP-(7-37). Prior exposure of cells to 100 nmol/liter GLP-(7-37) (10 min) did not alter the GIP-induced (10 nmol/liter) insulin release, but 100 nmol/liter GIP (10 min) reduced the insulin secretion during stimulation with 10 nmol/liter GIP by 56%. These data indicate that: 1) the GLP-I(7-37) receptor is subject to rapid and reversible homologous desensitization and, 2) the GLP-I(7-37) receptor on beta-cells is distinct from that of GIP. The recent finding of elevated GLP-I(7-36)amide levels in subjects with noninsulin-dependent diabetes suggest the possibility that a homologous desensitization of the GLP-I(7-37) receptor might contribute to the impaired insulin secretion in this disorder.     

The effects of hypothermia on human left ventricular contractile function during cardiac surgery.

OBJECTIVES: We investigated the interaction of heart rate (HR), temperature and contractility using a validated load independent method. BACKGROUND: Temperature manipulation is an integral part of cardiac surgery, and postoperative hypothermia is extremely common. Myocardial contraction is a series of enzymatic and physico-chemical reactions that may be differentially affected by temperature. METHODS: Ten patients undergoing coronary artery bypass grafting were studied during moderately hypothermic cardiopulmonary bypass. After conduit procurement and heparinization but before grafting, the patient was placed on cardiopulmonary bypass and rewarmed to 37 degrees C, and the left ventricle (LV) was instrumented with a conductance catheter allowing continuous pressure and volume measurement. The LV pressure volume relationship was examined to assess the contractility at 37, 35, 33 and 31 degrees C, with fixed atrial pacing (100 beats/min) in five patients and at 80 and 120 beats/min, at 33 and 37 degrees C in five patients. RESULTS: At a HR of 100 beats/min, lower temperature resulted in a highly significant decrease in maximal elastance (100% at 37 degrees C, 29 +/- 3.5% at 31 degrees C, p < 0.0001). At 37 degrees C, increasing HR increased contractility (80 beats/min 100%, 120 beats/min 205.9%, p = 0.0021); however, at 33 degrees C contractility fell with increasing HR (80 beats/min 100%, 120 beats/min, 53.7%, p = 0.0014). CONCLUSIONS: At normothermia LV contractility has a direct relationship with HR. In hypothermic conditions this relationship inverses. Clinical strategies maintaining higher HRs at colder temperatures result in reduced contractility. These factors are important in the management of cardiac surgical patients.     

降钙素基因相关肽刺激体外培养脊髓神经元细胞c-fos的表达

背景：内脏神经敏感性增高是胃肠道功能性疾病的重要发病机制之一，降钙素基因相关肽（CGRP）可能是其中重要的神经递质。目的：通过c-fos测定证实CGRP在脊髓内具有神经递质功能。方法：制备并培养大鼠脊髓神经元细胞，分别加入不同剂苗（10、20和40μl 100μmol／L）的CGRP，或经CGRP受体拮抗剂hCGRP8-37预处理后再加CGRP，行c-fos免疫组化染色和荧光定量聚合酶链反应（PCR）。结果：加入CGRP后，脊髓神经元的c-fos表达明显增加，但该作用可被CGRP受体挂号抗剂hCGRP8-37所阻断：c-fos的表达量与CGRP的浓度相关。结论：CGRP能激活脊髓神经元。     

Calcitonin gene-related peptide mediates nitroglycerin and sodium nitroprusside-induced vasodilation in feline cerebral arterioles.

The cerebral vasodilator response induced by topical nitroglycerin and nitroprusside was examined in cats equipped with cranial windows for the observation of the cerebral microcirculation. In cats subjected to chronic unilateral trigeminal ganglionectomy, the vasodilator responses to nitroprusside and nitroglycerin were markedly depressed on the denervated side. Application of a selective calcitonin gene-related peptide (CGRP) antagonist [CGRP(8-37)] on the innervated side reduced the response to nitrodilators to the same extent as seen on the denervated side. The vasodilator response to acetylcholine was unaffected by trigeminal ganglionectomy. CGRP(8-37) almost abolished the vasodilator response to nitroglycerin and sodium nitroprusside and to CGRP, but did not affect the response to adenosine or to adenosine diphosphate. Pretreatment with LY83583, a drug that lowers cyclic GMP levels, diminished the vasodilation to CGRP and to nitroprusside but not to adenosine. We conclude that the nitrovasodilators activate sensory fibers to release CGRP, which in turn relaxes cerebral vascular smooth muscle by activating guanylate cyclase. Hence, nitrovasodilators possess a novel mechanism of action within the cephalic circulation which may explain both the occurrence of vasodilation and headache.     

Microtubule-dependent effect of phorbol ester on the contractility of cytoskeleton of cultured fibroblasts.

The effect of the tumor promoter phorbol 12-myristate 13-acetate (PMA) upon the contractility of permeabilized cell models (cytoskeletons) of mouse fibroblasts was examined. Contraction was induced by incubation of cell models in a solution containing ATP and was assessed quantitatively by measuring alterations of the area of cell model projection on the substrate. Immunofluorescence microscopy was used to assess alterations of cytoskeleton morphology in the course of permeabilization and contraction. It was found that contractility of cell models from PMA-treated fibroblasts was considerably diminished as compared with the models from control fibroblasts. ATP induced only local contraction of certain zones of actin cortex in models from PMA-treated fibroblasts; it did not induce general contraction, characteristic of control models. Normal high contractility was characteristic of the models from the cells preincubated with PMA in combination with Colcemid. PMA is a specific activator of protein kinase C, one of the key enzymes of the membrane signal-transduction pathway. It is suggested that protein kinase C regulates contractility of actin cortex and that the pathway of this regulation has a microtubule-dependent stage blocked by Colcemid.     

Expression and pharmacological characterization of a stimulatory subtype of adenosine receptor in fetal chick ventricular myocytes.

Ventricular and atrial myocytes cultured from chick embryos 14 days in ovo were used as model systems to study cardiac adenosine receptors. In membranes of ventricular cultures, blocking of the A1-adenosine receptor pathway by the A1-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) or by pertussis toxin treatment of the myocyte resulted in a significant adenosine agonist-mediated stimulation of the adenylate cyclase activity. The maximal increases in adenylate cyclase activity caused by the equipotent or the A2-adenosine receptor-selective agonists (from 52.1 +/- 3% to 63 +/- 10% [mean +/- SEM]) were significantly greater than those caused by the A1-selective agonists (from 11 +/- 5% to 34.6 +/- 7%) (p less than 0.01, by t test, n = 4-8). However, in membranes of atrial myocytes, when A1-subtype had been blocked, the various adenosine agonists had no effect on the adenylate cyclase activity. Whether the stimulatory adenylate cyclase-coupled adenosine receptor is also capable of stimulating contractility in the intact ventricular myocyte was next investigated. In ventricular but not in atrial cells, the various adenosine agonists caused an increase in the contractile amplitude in the presence of DPCPX or in myocytes preexposed to pertussis toxin. The increase in contraction amplitude caused by each agonist was expressed as percent of maximum (maximum is the increase in contractility caused by 2.4 mM calcium). In the pertussis toxin-treated myocyte, the maximal increases caused by the equipotent or A2-agonists (NECA, MECA, CV-1808, and CGS21680, from 49.6 +/- 3% to 52.5 +/- 6%, n = 8-12) were significantly greater than those elicited by the A1-agonists (2-CADO, S-PIA, R-PIA, and DCCA, from 12 +/- 4% to 37 +/- 3%, n = 8) (p less than 0.05, by t test). These data demonstrated that a stimulatory adenosine receptor, likely the A2-adenosine receptor, was present on the ventricular but not the atrial myocytes and was linked directly to a stimulation of the cardiac contractility. The functional effects mediated by the A1-subtype became manifested in the presence of isoproterenol, as evidence by an inhibition of the isoproterenol-stimulated increases in adenylate cyclase activity and in cardiac contractility by adenosine agonists. Thus, both subtypes of adenosine receptors, each mediating opposing responses, were present on the ventricular myocytes, whereas only the A1-subtype was found in the atria. The presence of a stimulatory functional A2-adenosine receptor may help explain the absence of a direct negative inotropic response to adenosine in the ventricle.     

Calcitonin gene-related peptide: occurrence in pancreatic islets in the mouse and the rat and inhibition of insulin secretion in the mouse

The intrapancreatic cellular distribution and effects on basal and stimulated insulin secretion of the 37-amino-acid polypeptide, calcitonin gene-related peptide (CGRP), were investigated in the mouse. The cellular localization of CGRP was also studied in the rat pancreas. In both species, CGRP was demonstrated in pancreatic islet cells and nerve fibers. Immunocytochemical double staining experiments revealed the CGRP-immunoreactive cells in the mouse to be identical with a majority population of the insulin cells. In the rat, on the other hand, CGRP-immunoreactive cells were identical with somatostatin cells. CGRP-immunoreactive nerve fibers were observed, in both species, running in the exocrine parenchyma, particularly around blood vessels, and they were occasionally seen also within the islets. In in vivo experiments, CGRP was found to inhibit both basal and stimulated insulin secretion in the mouse. Thus, 6 min after the iv injection of CGRP (0.85 nmol/kg), plasma insulin levels were 13 +/- 2 (SE) microU/ml compared to 30 +/- 4 microU/ml in controls (P less than 0.01). At this dose level, CGRP inhibited the insulin secretory response to carbachol, leaving that to glucose unaffected. However, at a higher dose level (4.25 nmol/kg), CGRP inhibited glucose-induced insulin secretion as well. We conclude that CGRP occurs in islet cells and in intrapancreatic nerve fibers of both the mouse and the rat, and inhibits both basal and stimulated insulin secretion in vivo in the mouse.     

Ethanol dilates coronary arteries and increases coronary flow via transient receptor potential vanilloid 1 and calcitonin gene-related peptide

OBJECTIVES: Consumption of alcoholic beverages reduces the risk of coronary artery disease (CAD), and epidemiological studies have shown that ethanol per se is protective. However, the mechanism by which ethanol exerts protection is not fully known. Ethanol can stimulate neuropeptide-containing primary sensory neurons via the activation of transient receptor potential vanilloid 1 (TRPV1). Here, we have studied whether ethanol-mediated TRPV1 activation causes the release of calcitonin gene-related peptide (CGRP) that, via dilatation of coronary arteries and other mechanisms, may protect the heart from CAD. METHODS AND RESULTS: Ethanol caused a marked relaxation of small-sized porcine isolated coronary (0.008-2.37%, w/v) and human isolated gastro-epiploic (0.0008-2.37%, w/v) arteries in vitro, an effect that was abolished by capsaicin-desensitization, the TRPV1 antagonist capsazepine, and the CGRP receptor antagonist, CGRP(8-37). In guinea-pig isolated and perfused hearts, ethanol (0.079-0.79%, w/v) increased baseline coronary flow in a concentration-dependent manner: 0.237% ethanol doubled baseline coronary flow. This effect was also abolished by capsaicin-desensitization, capsazepine, and CGRP((8-37)). Finally, the ethanol-induced increase in CGRP release from guinea-pig isolated and perfused hearts and from slices of porcine coronary arteries was abolished by capsaicin-desensitization and by capsazepine. Similar functional and neurochemical results were obtained in all preparations with capsaicin. CONCLUSIONS: Ethanol, at low concentrations not dissimilar from those found in blood following low to moderate consumption of alcoholic beverages, releases CGRP within coronary arteries via stimulation of TRPV1 on perivascular sensory nerve terminals. Ethanol-induced release of CGRP may contribute to the reduction in the risk of CAD associated with alcohol consumption by various mechanisms, including the increase in coronary flow and arterial dilatation.     

Endogenous prostaglandin I2 regulates the neural emergency system through release of calcitonin gene related peptide

BACKGROUND: We previously reported that endogenous prostaglandin I(2), generated by a mild irritant, sensitised calcitonin gene related peptide (CGRP) containing sensory nerves and facilitated the release of CGRP and gastric mucosal protection against ethanol. Administration of capsaicin also inhibited ethanol induced gastric mucosal injury through immediate release of CGRP from primary sensory neurones, which is termed the neural emergency system. In the present study, we tested whether endogenous prostaglandin I(2) also modulates the cytoprotective action of capsaicin using prostaglandin I receptor knockout mice (IP(-/-)). METHODS: The stomachs of IP(-/-) or their wild-type counterparts (IP(+/+)), anaesthetised with urethane (1.225 g/kg), were doubly cannulated from the oesophageal and duodenal sides, and the gastric mucosa was perfused (1 ml/min) with physiological saline. Perfusate was changed to 50% ethanol alone, or 50% ethanol containing capsaicin (16 approximately 1600 micro M). The injured area was estimated at the end of each perfusion experiment. In some animals, CGRP-(8-37), a CGRP antagonist (0.3 mg/kg), or indomethacin (1 mg/kg) was intravenously injected before perfusion of 50% ethanol containing capsaicin. RESULTS: Capsaicin inhibited the injured area in a dose dependent manner. Fifty per cent ethanol containing capsaicin (480 micro M) immediately increased intragastric levels of CGRP although 50% ethanol alone did not. The protective action of capsaicin (480 micro M) against ethanol was completely abolished by intravenous injection of CGRP-(8-37). Indomethacin also inhibited the protective action of capsaicin, and this was accompanied by reduced levels of intragastric CGRP. Intragastric levels of prostaglandin E(2) were not increased by capsaicin treatment but those of 6-keto-prostaglandin F(1alpha), a metabolite of prostaglandin I(2), were markedly increased. No protective action of capsaicin was observed in IP(-/-) which lacked the ability to increase intragastric CGRP levels in response to ethanol containing capsaicin. The CGRP content of the stomach from untreated IP(-/-) did not differ from those in IP(+/+). Capsaicin (160 micro M) together with intragastric perfusion of beraprost sodium (PGI(2) analogue, 2.5 micro g/ml) showed enhanced protection against ethanol induced injury. This enhanced protection was completely blocked by intravenous injection of CGRP-(8-37). CONCLUSIONS: The present results suggest that endogenous prostaglandin I(2) enhances the protective action of the capsaicin mediated neural emergency system against ethanol induced gastric mucosal injury through enhancement of CGRP release.     

Decreased myocardial contractility in papillary muscles from atherosclerotic rabbits.

To determine the effect atherosclerosis has on myocardial contractility, we studied the contractile properties of right ventricular papillary muscles from 34 atherosclerotic and 17 control rabbits. We produced atherosclerosis by feeding for 2 to 8 months a diet of 5% lard, 5% peanut oil, 0.5% cholesterol, and 89.5% rabbit pellets. The controls received only rabbit pellets during the same time interval. Contracting isometrically 12 times per minute at 25 degrees C, muscles from the atherosclerotic rabbits developed tension at a lower maximum rate (max dT/dt), had a longer latency, and required longer to develop tension at the maximum rate and to develop peak tension. In isotonic contractions, they shortened with lower maximum velocities and required longer to accelerate to maximum velocity and to shorten maximally. We found no evidence that developed tension or distance shortened differed between the two groups of muscles. Raising the contraction frequency to 24 contractions per minute between the two groups of muscles. Raising the contraction frequency to 24 contractions per minute brought performance of the two groups of muscles closer in both types of contraction. Norepinephrine (1.5 x 10-5 M) nearly abolished differences between performance of the two groups. The loss of contractility correlates poorly with coronary and aortic atherosclerosis. It occurred early in the feeding of the atherogenic diet. We think it was due to a lipid-induced defect in the cardiac cell's handling of calcium.