Celiac Artery Vasculitis.

Isolated celiac artery vasculitis is an uncommon disease rarely reported in the Western literature. In this case report, we describe a 52-year-old Chinese male presenting with abdominal pain who was diagnosed with nonspecific celiac artery vasculitis and was successfully treated with a short course of oral corticosteroids.

Optimal management strategy for spontaneous isolated dissection of a visceral artery.

Objectives To describe our clinical experiences and recommend a management strategy for spontaneous isolated dissection of a visceral artery. Methods A retrospective study of patients from December 2005 to December 2015 was performed. Thirty-two patients had spontaneous isolated dissection of a visceral artery. Clinical features, computed tomography findings, the treatment method, and follow-up results were evaluated. Results There were 28 men and 4 women (mean age, 54 years). Dissection locations were the celiac artery in 10, superior mesenteric artery in 17, and celiac artery and superior mesenteric artery in 5 patients. Celiac artery stenosis existed with spontaneous isolated dissection of a visceral artery at a high rate. After diagnosis, the blood pressure of all patients was immediately controlled to a lower level. Three patients with arterial rupture and one patient with bowel infarction underwent operations for complications. Overall, the treatment of dissection involved drug therapy alone. The last follow-up computed tomography results of the true lumen residual ratio and the length of the dissected artery improved compared to the values on admission; the maximum diameter of the dissected artery did not enlarge. Eleven patients almost completely improved. No patients had any adverse event. Conclusions Most patients with spontaneous isolated dissection of a visceral artery can be first treated conservatively for dissection with strict blood pressure control and surveillance.

Medical therapy and intervention do not improve uncomplicated isolated mesenteric artery dissection outcomes over observation alone.

OBJECTIVE: Isolated dissection of the mesenteric vessels is rare but increasingly recognized. This study aimed to evaluate patient characteristics, primary treatment, and subsequent outcomes of mesenteric dissection using multi-institutional data. METHODS: All patients at participant hospitals between January 2003 and December 2015 with dissection of the celiac artery (or its branches) or dissection of the superior mesenteric artery (SMA) were included. Patients with an aortic dissection were excluded. Demographic, treatment, and follow-up data were collected. The primary outcomes included late vessel thrombosis (LVT) and aneurysmal degeneration (AD). RESULTS: Twelve institutions identified 227 patients (220 with complete treatment records) with a mean age of 55 ± 12.5 years. Median time to last follow up was 15 months (interquartile range, 3.8-32). Most patients were men (82% vs 18% women) and symptomatic at presentation (162 vs 65 asymptomatic). Isolated SMA dissection was more common than celiac artery dissection (n = 158 and 81, respectively). Concomitant dissection of both arteries was rare (n = 12). The mean dissection length was significantly longer in symptomatic patients than in asymptomatic patients in both the celiac artery (27 vs 18 mm; P = .01) and the SMA (64 vs 40 mm; P < .001). Primary treatment was medical in 146 patients with oral anticoagulation or antiplatelet therapy (n = 76 and 70, respectively), whereas 56 patients were observed. LVT occurred in six patients, and 16 patients developed AD (3% and 8%, respectively). For symptomatic patients without evidence of ischemia (n = 134), there was no difference in occurrence of LVT with medical therapy compared with observation alone (9% vs 0%; P = .35). No asymptomatic patient (n = 64) had an episode of LVT at 5 years. AD rates did not differ among symptomatic patients without ischemia treated with medical therapy or observed (9% vs 5%; P = .95). Surgical or endovascular intervention was performed in 18 patients (3 ischemia, 13 pain, 1 AD, 1 asymptomatic). Excluding the patients treated for ischemia, there was no difference in LVT with surgical intervention vs medical management (one vs five; P = .57). CONCLUSIONS: Asymptomatic patients with isolated mesenteric artery dissection may be observed and followed up with intermittent imaging. Symptomatic patients tend to have longer dissections than asymptomatic patients. Symptomatic isolated mesenteric artery dissection without evidence of ischemia does not require anticoagulation and may be treated with antiplatelet therapy or observation alone.

The BB2 receptor antagonist BW2258U89 attenuates the feeding responses evoked by exogenous gastrin releasing peptide-29.

This confirmatory work is aimed to test that the hypothesis that the gastrin releasing peptide (GRP) receptor - the BB2 receptor - is necessary for reduction of meal size (MS) and prolongation of the intermeal interval (IMI) by the small and the large forms of GRP in the rat, GRP-10 and GRP-29, and to confirm the sites of action regulating such responses - the vascular bed of the celiac artery (CA, supplying stomach and upper duodenum). To pursue these aims we measured first MS and IMI length in response to GRP-10 and GRP-29 (0, 0.5nmol/kg) infused in the CA (n=8 rats) and the cranial mesenteric artery (CMA, supplying the small and part of the large intestine, n=8 rats) in near spontaneously free feeding rats pretreated with the BB2 receptor antagonist BW2258U89 (0.1mg/kg) in the same arteries prior to the onset of the dark cycle. We found that GRP-29, but not GRP-10, infused by the CA reduced MS and prolonged the IMI by decreasing meal latency and meal duration and the BB2 receptor antagonist BW2258U89 infused in the same artery attenuated these responses. These results suggest that the BB2 receptor is necessary for reduction of MS and prolongation of the IMI by exogenous GRP-29, and the vascular bed of the CA, stomach and upper duodenum, contains sites of action regulating these feeding responses.

Cholecystokinin-33, but not cholecystokinin-8 shows gastrointestinal site specificity in regulating feeding behaviors in male rats.

Two separate experiments were performed to localize the gastrointestinal sites of action regulating meal size (MS), intermeal interval (IMI) length and satiety ratio (SR, IMI/MS) by cholecystokinin (CCK) 8 and 33. Experiment 1: CCK-8 (0, 0.05, 0.15, 0.25nmol/kg) was infused in the celiac artery (CA, supplies stomach and upper duodenum) or the cranial mesenteric artery (CMA, supplies small and part of the large intestine) prior to the onset of the dark cycle in free feeding, male Sprague Dawley rats and MS (normal rat chow), IMI and SR were recorded. Experiment 2: CCK-33 (0, 0.05, 0.15, 0.25nmol/kg) were infused in the CA or the CMA, under the same experimental conditions above, and MS, IMI and SR were recorded. Experiment 1 found that CCK-8 reduces MS, prolongs the IMI and increases the SR at sites supplied by both arteries. Experiment 2 found that CCK-33 reduces MS and increases the SR at sites supplied by the CMA. We conclude that in male rats the feeding behaviors evoked by CCK-33, but not CCK-8, are regulated at specific gastrointestinal sites of action.

Exogenous glucagon-like peptide-1 acts in sites supplied by the cranial mesenteric artery to reduce meal size and prolong the intermeal interval in rats.

Three experiments were done to better assess the gastrointestinal (GI) site(s) of action of GLP-1 on food intake in rats. First, near-spontaneous nocturnal chow meal size (MS), intermeal intervals (IMI) length and satiety ratios (SR = MS/IMI) were measured after infusion of saline, 0.025 or 0.5 nmol/kg GLP-1 into the celiac artery (CA, supplying the stomach and upper duodenum), cranial mesenteric artery (CMA, supplying small and all of the large intestine except the rectum), femoral artery (FA, control) or portal vein (PV, control). Second, infusion of 0.5 nmol/kg GLP-1 was tested after pretreatment with the GLP-1 receptor (GLP-1R) antagonist exendin-4(3-39) via the same routes. Third, the regional distribution of GLP-1R in the rat GI tract was determined using rtPCR. CA, CMA and FA GLP-1 reduced first MS relative to saline, with the CMA route more effective than the others. Only CMA GLP-1 prolonged the IMI. None of the infusions affected second MS or later eating. CA and CMA GLP-1 increased the SR, with the CMA route more effective than the CA route. CMA exendin-4 (3-39) infusion reduced the effect of CMA GLP-1. Finally GLP-1R expression was found throughout the GI tract. The results suggest that exogenous GLP-1 acts in multiple GI sites to reduce feeding under our conditions and that GLP-1R in the area supplied by the CMA, i.e., the small and part of the large intestine, plays the leading role.

Intravenous vasopressin for the prevention of nontarget gastrointestinal embolization during liver-directed cancer treatment: experimental study in a porcine model.

PURPOSE: The aim of this study was to evaluate the potential for intravenous vasopressin to reduce the risk of nontarget gastrointestinal embolization during transcatheter liver-directed cancer therapies in a porcine model. MATERIALS AND METHODS: An angiographic catheter was used to select the celiac or common hepatic artery under fluoroscopic guidance in six anesthetized pigs. After angiography of the hepatic and splanchnic territories was performed, technetium-99m macroaggregated albumin ((99m)Tc-MAA) was injected through the catheter. Serial arteriograms were obtained before, every 5 minutes during, and after peripheral intravenous vasopressin infusion at 0.4 U/min for a minimum of 20 minutes. After 10 minutes of infusion, indium-111 ((111)In)-MAA was injected through the arterial catheter. Quantitative comparisons of liver and gastrointestinal activity using dual-isotope single-photon emission computed tomography (SPECT)/CT imaging were performed. RESULTS: Catheter angiography demonstrated reduced blood flow to the splanchnic vasculature while maintaining blood flow through the hepatic arteries during vasopressin infusion. Angiographic findings correlated with the relative distribution of (99m)Tc-MAA (before the vasopressin infusion) and (111)In-MAA (after the vasopressin infusion) on SPECT/CT. The increased ratio of liver to gastrointestinal tract activity during the vasopressin infusion was statistically significant (6.2:11.4, respectively; P = .018). CONCLUSIONS: Intravenous vasopressin reduces arterial blood flow to the splanchnic vasculature while preserving hepatic arterial blood flow in a healthy porcine model. Intraprocedural vasopressin administration has the potential to benefit liver-directed cancer therapies by enhancing tumor targeting as well as preventing the unintended delivery of bland embolic, chemoembolic, or radioembolic agents into the gastrointestinal vascular territories.

Proteus Takayasu's arteritis with unusual intracranial granulomatosis as initial manifestation.

Takayasu's arteritis (TA) is an inflammatory vasculitis of aorta and its branches, its low incidence limited our recognition to this entity. We sometimes can confuse this disease with polyarteritis nodosa and other vasculitis when no conventional "big artery" involved in TA cases. Here we report a 26-year-old man with Takayasu's arteritis who presented with a provisional intracranial granulomatosis first and then saccular aneurysms between celiac trunk and arteria hepatica communis and many other proteus manifestations, which is seldom described before.

Effects of fenoldopam mesylate infusion on splanchnic perfusion after myocardial revascularization on cardiopulmonary bypass: an ultrasound Doppler study.

OBJECTIVES: To measure the effects of fenoldopam mesylate infusion on splanchnic blood flow in patients undergoing myocardial revascularization with cardiopulmonary bypass. DESIGN: An experimental observational study. SETTING: A single-institution community hospital. PARTICIPANTS: Eighteen patients undergoing on-pump coronary artery bypass graft surgery. INTERVENTIONS: Fenoldopam mesylate infusion (0.1 µg/kg/min). MEASUREMENTS AND MAIN RESULTS: Blood flow through the celiac artery, superior mesenteric artery, portal vein and hepatic artery were assessed by means of Doppler measurements. The main hemodynamic variables were measured using echocardiography. The infusion of fenoldopam significantly increased the blood flow through both celiac and superior mesenteric arteries by decreasing vascular resistance. The percentage of cardiac output directed to these 2 vessels increased significantly; the increase through the superior mesenteric artery was greater compared with the celiac artery. Portal vein and hepatic artery blood flow also consistently increased. No significant variations were observed with respect to hemodynamic variables. CONCLUSIONS: The infusion of fenoldopam increased the flow through the celiac artery and superior mesenteric artery; the effect was higher for the latter. These changes did not affect the hemodynamic variables.

Cod CGRP and tachykinins in coeliac artery innervation of the Atlantic cod, Gadus morhua: presence and vasoactivity.

The presence and vasoactive effects of native calcitonin gene-related peptide (CGRP), substance P (SP), and neurokinin A (NKA) were studied on isolated small branches of the coeliac artery from Atlantic cod, Gadus morhua, using immunohistochemistry and myograph recordings, respectively. Immunohistochemistry revealed nerve fibers containing CGRP- and SP/NKA-like material running along the wall of the arteries. CGRP induced vasorelaxation of precontracted arteries with a pD(2) value of 8.54 +/- 0.17. Relaxation to CGRP (10(-8) M) was unaffected by L-NAME (3 x 10(-4) M) and indomethacin (10(-6) M) suggesting no involvement of nitric oxide or prostaglandins in the CGRP-induced relaxation. SP and NKA (from 10(-10) to 3 x 10(-7) M) contracted the unstimulated arteries at concentrations from 10(-8) M and above in 42% and 33%, respectively, of the vessels. It is concluded that the innervation of the cod celiac artery includes nerves expressing CGRP-like and tachykinin-like material, and that a vasodilatory response to CGRP is highly conserved amongst vertebrates while the response to tachykinins is more variable.

Effects of a divided high loading dose of caffeine on circulatory variables in preterm infants.

BACKGROUND: A single high loading dose of 25 mg/kg caffeine has been shown to be effective for the prevention of apnoea, but may result in considerable reductions in blood flow velocity (BFV) in cerebral and intestinal arteries. OBJECTIVE: To assess the effects of two loading doses of 12.5 mg/kg caffeine given four hours apart on BFV in cerebral and intestinal arteries, left ventricular output (LVO), and plasma caffeine concentrations in preterm infants. DESIGN: Sixteen preterm neonates of <34 weeks gestation were investigated one hour after the first oral dose and one, two, and 20 hours after the second dose by Doppler sonography. RESULTS: The mean (SD) plasma caffeine concentrations were 31 (7) and 29 (7) mg/l at two and 20 hours respectively after the second dose. One hour after the first dose, none of the circulatory variables had changed significantly. One hour after the second caffeine dose, mean BFV in the internal carotid artery and anterior cerebral artery showed significant reductions of 17% and 19% (p = 0.01 and p = 0.003 respectively). BFV in the coeliac artery and superior mesenteric artery, LVO, PCO2, and respiratory rate had not changed significantly. Total vascular resistance, calculated as the ratio of mean blood pressure to LVO, had increased significantly one and two hours after the second dose (p = 0.049 and p = 0.023 respectively). CONCLUSION: A divided high loading dose of 25 mg/kg caffeine given four hours apart had decreased BFV in cerebral arteries after the second dose, whereas BFV in intestinal arteries and LVO were not affected.

The Effect of Milrinone on Splanchnic and Cerebral Perfusion in Infants With Congenital Heart Disease Prior to Surgery: An Observational Study.

Despite the advancement in the postoperative care of neonates with congenital heart disease (CHD), there is little information on preoperative management of systemic and regional hemodynamics, which may be related to outcomes. We aimed to determine the preoperative effect of milrinone, a phosphodiesterase III inhibitor, on cardiac output and splanchnic and cerebral perfusion in neonates with CHD. Neonates with CHD requiring cardiac surgery were enrolled in a prospective, single-blinded study once a clinical decision of starting milrinone (0.75 µg/kg per minute intravenously) using institutional criteria was made. Demographic and clinical variables and outcomes were recorded. Combined cardiac output and measures of splanchnic (superior mesenteric and celiac arteries) and cerebral (anterior and middle cerebral arteries) perfusion were determined by Doppler studies at 0, 6, 24, and 48 h after milrinone infusion. Investigators were unaware of intervention time points and patients in analyzing blood flow measurements. Seventeen term (39.2 ± 1.3 weeks) neonates were included with hypoplastic left-sided heart syndrome (78.5%) as the most common diagnosis. Combined cardiac output increased by 28% within 48 h (613 ± 154 vs. 479 ± 147 mL/kg per minute at baseline, P < 0.05). Superior mesenteric artery mean velocity increased at 6 h and throughout 48 h of milrinone infusion (P < 0.05). Peak and mean velocities at cerebral arteries increased with milrinone infusion (P < 0.05~0.08), and the corresponding changes at celiac artery were modest. There were no significant changes in splanchnic and cerebral resistive and pulsatility indices during milrinone infusion. Milrinone increases cardiac output with concurrent effects on splanchnic and cerebral blood flows during the short-term preoperative use in neonates with CHD.

Different flow regulation mechanisms between celiac and mesenteric vascular beds in conscious rats.

The aims of this study were to elucidate the vasoconstrictor mechanism that mediates the changes in celiac and mesenteric vascular resistances during vasoconstriction and hypertension induced by ganglionic blockade and to explore the preferential mechanism that contributes to the elevation of arterial pressure in conscious spontaneously hypertensive rats (SHR). In conscious SHR and normotensive control rats, blood flow and arterial pressure were measured with an implanted electromagnetic flow probe and an indwelling arterial catheter. Peripheral vascular resistance was calculated as arterial pressure divided by regional flow. Celiac contribution to the hypertension in SHR was below average for the entire body and was smaller than that from the superior mesenteric bed. The increase of mesenteric resistance with arterial pressure elevation after ganglionic blockade suggests that mesenteric blood flow is regulated by a stretch-dependent myogenic mechanism, whereas celiac blood flow is regulated preferentially by the sympathetic neural mechanism. It is speculated that the flow superregulation in the mesenteric bed in SHR is due to the enhanced myogenic response and contributes to the early stage of hypertension.

Selective inhibition by gossypol of endothelium-dependent relaxations augments relaxations to glyceryl trinitrate in rabbit coeliac artery.

1 Acetylcholine, substance P, prostaglandin E1 and the nitrovasodilator glyceryl trinitrate induced concentration-dependent relaxations of endothelium-intact strips of rabbit coeliac artery precontracted with noradrenaline. 2 Endothelium-denuded strip preparations contracted to acetylcholine and showed no response to substance P. The relaxant response to prostaglandin E1 was unimpaired after removal of endothelium, whereas the response to glyceryl trinitrate was increased. 3 A 20 min exposure of endothelium-intact strips to gossypol, an irreversible inhibitor of the production and/or release of endothelium-derived relaxing factor, abolished vasodilatation in response to the endothelium-dependent agents acetylcholine and substance P, did not change relaxations to prostaglandin E1, but significantly enhanced relaxations in response to glyceryl trinitrate. 4 In view of the assumed common mechanism of action of endothelium-derived relaxing factor and nitrovasodilators, these results suggest an interference of the two active principles at the level of the vascular smooth muscle cell.

Actions of bradykinin and related peptides on rabbit coeliac artery rings.

1. Rabbit coeliac artery rings were mounted in tissue baths containing Krebs solution at 37 degrees C in order to determine whether their response to bradykinin is initiated by B1- or B2-receptors. Tension was recorded isometrically. 2. Phenylephrine contracted the tissue. Subsequent addition of bradykinin or des Arg10-kallidin caused relaxation which was not dependent on an intact endothelium. Des Arg10-kallidin, a B1-receptor selective agonist, was more potent than bradykinin. 3. [beta-Thienyl alanyl6,9, D-Phe8]-kallidin and [Leu9]-des Arg10-kallidin antagonized bradykinin and des Arg10-kallidin. [Leu9]-des Arg10-kallidin, a B1-receptor selective antagonist, was more potent than [Thi6,9, D-Phe8]-kallidin, a less selective drug that acts on both B1- and B2-receptors. 4. Kinin-induced relaxation was reversibly antagonized by ibuprofen (a cyclo-oxygenase inhibitor) and by 5-(N,N-hexamethylene)amiloride (an inhibitor of Na+/H+ exchange). Ibuprofen caused a parallel shift to the right of a semi-logarithmic plot of the agonist concentration-effect relationship, whereas the amiloride analogue depressed the maximum response and reduced the slope. 5. We conclude that bradykinin and des Arg10-kallidin relax rabbit coeliac artery by combining with B1-receptors. The response is mediated by a cyclo-oxygenase product and may be influenced by cellular Na+/H+ exchange.

Adenylate cyclase-mediated vascular responses of rabbit aorta, mesenteric artery and skin microcirculation.

1. The importance of adenylate cyclase-mediated vascular relaxation in the macro and microcirculation was assessed in rabbit aortic and coeliac artery bioassay rings in vitro and skin microvessels in vivo. 2. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP38), the beta-agonist, isoprenaline, and the prostaglandins, PGE1 and PGE2, were compared with the activity of nitroprusside, which acts by stimulating guanylate cyclase. 3. In aortic tissue the relative relaxant potencies were (-log M EC50, 100% = response to nitroprusside 10(-6) M): nitroprusside 7.0, PACAP38 6.8, isoprenaline 6.3; PGE1 and PGE2 were weak constrictors. In coeliac artery rings relative potencies were (-log M EC50, 100% = response to nitroprusside 10(-5) M): PACAP38 6.6, PGE1 6.6, nitroprusside 6.5, PGE2 4.9, and isoprenaline 4.3. 4. Comparative potencies when injected into anaesthetized rabbit skin in vivo were (-log mol/site required to increase blood red cell flux by 75%): PACAP38 13.0, PGE2 10.7, isoprenaline 9.7, PGE1 9.1, nitroprusside < 7. 5. Nitroprusside, the most effective relaxant tested in the aorta, was 10(7) fold less potent than PACAP in its effect on skin blood flow. PGE1 and PGE2 were constrictors of the aorta, of intermediate effect in the coeliac artery, but potent vasodilators of the microcirculation. 6. In this model, the importance of adenylate cyclase-mediated vascular relaxation increases with decreasing vessel size.

Evidence for both histamine H1- and H2-receptors in the gastric vasculature of the cat.

1 Experiments have been done to study the gastric vascular response to histamine given intra-arterially in the cat.2 In experiments utilising pump perfusion of the stomach at constant flow rates, rapid intra-arterial injections of histamine elicited dose-dependent vasodilatation. The dose-response curve to histamine was displaced to the right by mepyramine and further to the right by mepyramine plus cimetidine. Cimetidine alone did not displace the histamine dose-response curve. This interaction between histamine and histamine antagonists is very similar to the interaction observed in other vascular beds.3 Intra-arterial infusions of histamine also caused vasodilatation with increased gastric blood flow, measured with an electromagnetic flow probe. Mepyramine reduced the immediate increase in blood flow during each infusion, although responses in the later stages of the infusions were unaltered. Cimetidine had no effect on the immediate response but reduced sustained responses to histamine. Treatment with mepyramine and cimetidine was required to abolish histamine responses.4 Infusions of 2-(2-aminoethyl) pyridine and dimaprit also increased gastric blood flow.5 These results indicate the involvement of both H(1)- and H(2)-receptors in histamine-induced gastric vasodilatation. There appears to be a time-base in the interaction between histamine and vascular histamine receptors; H(1)-receptor responses preceding H(2)-receptor responses.

Effects of sodium and calcium concentrations on the potentiation by indomethacin of the responses of rabbit mesenteric and coeliac arteries to vasoconstrictor agonists.

The contractile responses of the rabbit isolated coeliac and mesenteric arteries to five agonists (angiotensin, adrenaline, histamine, acetylcholine and 5-hydroxytryptamine), but not to K+, were potentiated by indomethacin (8.4 microM) The potentiation was similar whether indomethacin was added 1 h before or during the response to the agonist. The agonists that were more potentiated by indomethacin were also more dependent on the Ca2+ concentration in the medium, for their contractile action. Prostaglandin E2 in low concentrations (micromolar) did not affect the resting tone but relaxed the agonist-contracted arteries both in normal and in Ca2+-free medium. No prostaglandin E (PGE)-like substances were detected in the perfusate of arteries contracted by angiotensin. Reduction of the external Na+ concentration to 80 mM resulted in potentiation of the responses to agonists (angiotensin and adrenaline), but not to K+, and in this Na+-deficient medium potentiation by indomethacin was greatly reduced. These results suggest that potentiation by indomethacin of the arteries' responses to vasoactive substances may result from that drug's inhibitory action on sodium influx and consequent increase in calcium entry through receptor-operated channels.

Interactions of iloprost and sodium nitroprusside on vascular smooth muscle and platelet aggregation.

1. The aim of the study was to assess and quantify any synergism occurring between the stable analogues of prostacyclin (iloprost) and nitric oxide (sodium nitroprusside) with respect to both relaxation of vascular smooth muscle and inhibition of platelet aggregation in the rabbit. 2. Iloprost (0.3-3 ng ml-1) and sodium nitroprusside (0.3-3 ng ml-1) caused dose-dependent relaxation of the rabbit mesenteric and coeliac arteries. 3. Iloprost (0.3-30 ng ml-1) and sodium nitroprusside (0.03-30 micrograms ml-1) caused dose-dependent inhibition of rabbit platelet aggregation induced by adenosine diphosphate or collagen. 4. In combination, iloprost and sodium nitroprusside caused an inhibition of platelet aggregation that was 2-3 fold greater than would be expected by summation, while no such potentiation was observed on vascular smooth muscle. 5. Thus, our results indicate that under physiological conditions the mediators prostacyclin and endothelium-derived relaxing factor (NO) can exert a synergistic action on platelets, but have only an additive effect on vascular smooth muscle.

Coeliac haemodynamic effects of endothelin-1, endothelin-3, proendothelin-1 [1-38] and proendothelin-3 [1-41] in conscious rats.

1. Conscious, chronically-instrumented, Long Evans rats were given bolus doses of endothelin-1, endothelin-3 (both at 0.01 and 0.1 nmol kg-1), proendothelin-1 [1-38] and proendothelin-3 [1-41] (both 0.1 and 1 nmol kg-1) in order to compare their effects on coeliac haemodynamics, because it has been reported that, in conscious dogs, endothelin-1 has paradoxical, prolonged hyperaemic vasodilator effects in this vascular bed. Measurements were made also of mesenteric and hindquarters haemodynamics for comparison. In a separate experiment, endothelin-1 (0.1 nmol kg-1) was given before and 20 min after the onset of an infusion of mecamylamine (50 mumol kg h-1) to ensure that the responses measured were not confounded by rapid reflex changes in autonomic activity. 2. None of the peptides caused any increases in coeliac flow or any sustained rises in coeliac vascular conductance, although such changes were clear-cut in the hindquarters vascular bed following the higher dose of endothelin-1 and endothelin-3. In animals treated with mecamylamine the regional haemodynamic effects of the higher dose endothelin-1 were not different from those in animals with intact baroreflexes. 3. Although the lower dose of both endothelin-1 and endothelin-3 caused less marked coeliac, than mesenteric vasoconstriction, this difference was not apparent with the higher dose of the peptides, or with proendothelin-1 [1-38]. However, proendothelin-3 [1-41] had less marked coeliac and hindquarters vasoconstrictor effects than proendothelin-1 [1-38], in spite of both peptides causing similar changes in mesenteric haemodynamics.These differences could have been due to regional differences in the conversion of proendothelin-l [1-38] and proendothelin-3 [1-41] to endothelin-l and endothelin-3,respectively. Our findings contradict the proposition that exogenous proendothelin-3[1-41] is not converted into endothelin-3 in vivo.4. Since, in contrast to endothelin-1 and endothelin-3, proendothelin-1 [1-38] and proendothelin-3 [1-41] caused only small hindquarters vasodilatations, but large vasoconstrictions, it is feasible that the vasodilator responses to exogenous endothelin-l and endothelin-3 are pharmacological phenomena, and that, in vivo, the production of endothelins from proendothelins exerts widespread vasoconstrictor effects.