(1/431) In vitro simultaneous measurements of relaxation and nitric oxide concentration in rat superior mesenteric artery.
1. The relationship between nitric oxide (NO) concentration measured with an NO-specific microelectrode and endothelium-dependent relaxation was investigated in isolated rat superior mesenteric artery contracted with 1 microM noradrenaline. 2. Acetylcholine (10 microM) induced endothelium-dependent simultaneous increases in luminal NO concentration of 21 +/- 6 nM, and relaxations with pD2 values and maximum of 6.95 +/- 0.32 and 97.5 +/- 0.7 % (n = 7), respectively. An inhibitor of NO synthase, N G-nitro-L-arginine (L-NOARG, 100 microM) inhibited the relaxations and increases in NO concentration induced by acetylcholine. 3. Oxyhaemoglobin (10 microM) reversed the relaxations and increases in NO concentrations induced by acetylcholine, S-nitroso-N-acetylpenicillamine (SNAP) and S-morpholino-sydnonimine (SIN-1), but not the relaxations induced with forskolin. Oxyhaemoglobin also decreased the NO concentration below baseline level. 4. In the presence of L-NOARG (100 microM), a small relaxation to acetylcholine (10 microM) of noradrenaline-contracted segments was still seen; oxyhaemogobin inhibited this relaxation and decreased the NO concentration by 14 +/- 4 nM (n = 4). 5. The NO concentration-relaxation relationship for acetylcholine resembled that for SNAP and SIN-1 more than for authentic NO. Thus while 7-17 nM NO induced half-maximal relaxations in response to SNAP or SIN-1, 378 +/- 129 nM NO (n = 4) was needed for half-maximal relaxation to authentic NO. 6. The present study provides direct evidence that the relaxation of the rat superior mesenteric artery with the endothelium-dependent vasodilator acetylcholine is correlated to the endogeneous release of NO. The study also suggests that NO mediates the L-NOARG-resistant relaxations in this artery, and that there is a basal NO release. (+info)
(2/431) Antegrade visceral revascularisation via a thoracoabdominal approach for chronic mesenteric ischaemia.
OBJECTIVES: It has been suggested that patients with chronic visceral ischaemia are elderly and emaciated hence they may not tolerate antegrade visceral revascularisation via a thoracoabdominal approach. There are no studies to support this assumption. The purpose of this study is to assess the efficacy of this approach for the treatment of chronic visceral ischaemia. METHODS: Between 1988 and 1996, 10 patients underwent antegrade visceral revascularisation for chronic visceral ischaemia via a thoracoabdominal approach and were followed-up for a mean of 40 months. Eight patients were treated with aorto superior mesenteric artery bypass and implantation of the coeliac axis in the graft and two patients with aorto superior mesenteric bypass alone. Graft patency was monitored with duplex scanning. RESULTS: There were no postoperative deaths in this series. Two patients developed postoperative pulmonary infections and required intubation for a short period of time. All patients were discharged after a mean of 17 days (range 7-38). Follow up with duplex scanning revealed that all grafts were patent. One patient developed a high grade anastomotic stenosis which was followed by recurrence of the symptoms. This was dilated on three occasions by balloon angioplasty within a period of 17 months. On the last occasion a stent was placed and since the patient remains asymptomatic. CONCLUSIONS: Antegrade visceral revascularisation via a thoracoabdominal approach is a durable and effective method of relieving symptoms of chronic visceral ischaemia. The low morbidity in this series justifies larger studies in order to establish the true incidence of complications. (+info)
(3/431) Celiomesenteric anomaly with concurrent aneurysm.
We describe a rare case of a celiomesenteric anomaly with concurrent aneurysm. The patient, a 53-year-old man, had no abdominal pain or discomfort. The presence of a celiac artery aneurysm was suspected on the basis of the results of abdominal computerized tomographic scanning and echo ultrasound scanning performed because of proteinuria. Intra-arterial digital subtraction angiographic results showed the anomaly and aneurysm. Because of the risk of rupture of the aneurysm, the lesion was repaired surgically, with the placement of an interpositional prosthetic graft. We found no previous reports of celiomesenteric anomaly with concurrent aneurysm repaired with prosthetic graft. (+info)
(4/431) NO overproduction by eNOS precedes hyperdynamic splanchnic circulation in portal hypertensive rats.
Chronic high blood flow and the hyperdynamic circulatory syndrome in portal hypertension are associated with endothelial constitutive nitric oxide (NO) synthase (eNOS) upregulation and increased NO release. In portal vein-ligated (PVL) rats the splanchnic circulation is not yet hyperdynamic on day 3 postoperatively. In vitro perfused superior mesenteric arteries (SMAs) of day 3 PVL and sham rats were challenged with increasing flow rates or the alpha-adrenoreceptor agonist methoxamine (30 and 100 microM) before and after incubation with the NO inhibitor, Nomega-nitro-L-arginine (L-NNA, 10(-4) M). Perfusate NO metabolite (NOx) concentrations were measured by chemiluminescence. PVL rats expressed a significant hyporesponsiveness to increases in flow rate or methoxamine that was overcome by incubation with L-NNA. The PVL vasculature showed significantly higher slopes of NOx production vs. flow-induced shear stress, higher increases in perfusate NOx concentration in response to methoxamine, and higher eNOS protein levels (Western blot) compared with sham rats. In conclusion, eNOS-upregulation and increased NO release by the SMA endothelium occur before the development of the hyperdynamic splanchnic circulation, suggesting a primary role of NO in the pathogenesis of arterial vasodilatation. (+info)
(5/431) Does endothelin-1 reduce superior mesenteric artery blood flow velocity in preterm neonates?
AIM: To compare plasma endothelin-1 (ET-1) concentrations in preterm neonates from pre-eclamptic and normal mothers; and to evaluate whether ET-1 has a role in altered arterial blood flow velocity. METHODS: Umbilical arterial blood and neonatal arterial blood were sampled on days 1 and 3 for gas analysis and measurement of plasma ET-1. Doppler ultrasonography of the middle cerebral, renal, and superior mesenteric arteries (SMA) was performed. RESULTS: Neonates in the pre-eclampsia (n = 18) and control (n = 18) groups had mean (SD) gestational ages of 31.1 (2.5) weeks and 30.4 (2.1) weeks; their birth-weights were 1432 (SD 676) g and 1692 (SD 500) g, respectively. In the pre-eclampsia group mean umbilical arterial PO2 was lower--1.88 (0.75) kPa compared with 3.27 (1.41) kPa (p < 0.01)--and mean plasma ET-1 concentration was higher in the umbilical artery--40.6 (SD 15.0) compared with 30.5 (SD 13.8) pg/ml (p = 0.04) and day 1 blood--54.9 (35.0) pg/ml compared with 33.6 (14.6) pg/ml (p = 0.03). Middle cerebral artery peak systolic velocity was higher and SMA time averaged, peak systolic, and mean peak velocities were lower in the pre-eclampsia group. SMA time averaged velocity was inversely related to plasma ET-1 concentration. CONCLUSION: The association between increased production of ET-1 and reduction in SMA time averaged velocity suggests a possible mechanism for hypoperfusion of the intestinal wall in neonates. (+info)
(6/431) Effect of caffeine on neonatal splanchnic blood flow.
Doppler ultrasound was used to study the effect of the first intravenous dose of caffeine on splanchnic haemodynamics in preterm neonates. Peak systolic velocity in the superior measenteric artery and coeliac axis was significantly reduced for 6 hours after caffeine infusion. The effect of this reduction in blood flow to the neonatal gut is not known. (+info)
(7/431) Shear stress-induced nitric oxide antagonizes adenosine effects on intestinal metabolism.
The influence of nitric oxide (NO) on adenosine-induced metabolic effects was studied in the intestine. Blood flow supplied an in situ- isolated segment of small intestine in anesthetized cats via the superior mesenteric artery (SMA) and was controlled by a vascular circuit. The SMA and portal samples were taken for analysis of oxygen and lactate. Adenosine (0.4 mg. kg-1. min-1, intra-SMA) reduced oxygen consumption by 25.1 +/- 2.9 from 73.1 +/- 10.8 micromol. min-1. 100 g-1 and increased lactate production by 13.3 +/- 3.0 from 12.8 +/- 4.6 micromol. min-1. 100 g tissue-1 during constant-flow (CF, decreased shear stress) but not during constant-pressure (CP, increased shear stress) perfusion. Blockade of NO synthase using Nomega-nitro-L-arginine methyl ester did not affect the metabolic effects of adenosine during CF but eliminated the differences seen between CP and CF perfusion. A NO donor, 3-morpholinosydnonimine, attenuated the metabolic effects of adenosine during CF perfusion. The results suggested that shear-induced NO antagonized metabolic effects of adenosine but that the inhibition of vascular effects by NO was not shear dependent since it occurred in both CP and CF perfusion. (+info)
(8/431) Physiological control of splanchnic blood flow by adrenaline: studies during acute hypoglycaemia in man.
Superior mesenteric artery blood flow (SMABF) increases significantly during and after the hypoglycaemia reaction in healthy humans. To investigate the mechanisms controlling this phenomenon, SMABF and plasma catecholamines were measured in healthy human volunteers. In 10 controls, hypoglycaemia was induced by insulin infusion (2.5 m-units.min-1.kg-1). In six subjects, beta-blockade by propranolol infusion (0.7 microgram.min-1.kg-1) preceded insulin infusion and was continued throughout the study. Following the hypoglycaemia reaction, the glucose nadir was similar in both groups. In controls, increases in SMABF [42.4+/-6.1% (mean+/-S.E.M.); P<0. 001], cardiac output (34.3+/-2.3%; P<0.001) and pulse rate (from 63. 9+/-2.7 to 82.5+/-3.1 beats/min; P<0.001) occurred. Superior mesenteric artery resistance fell by 32.4+/-3.3% (P<0.001). Under beta-blockade, decreases in SMABF (34.8+/-2.9%; P<0.001) and pulse rate (from 59.5+/-0.2 to 51.8+/-2.2 beats/min; P<0.001) occurred. Superior mesenteric artery resistance increased (peak +30.8+/-12.3%; not significant). Subjects showed greater increases in adrenaline (P<0.006) and noradrenaline (P<0.022) concentrations than controls. Mesenteric hyperaemia associated with hypoglycaemia in man appears to be mediated by a beta-adrenergic mechanism that is activated by increased circulating levels of adrenaline. (+info)