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At least 19 recordsLinked to original sources
PubMed1992

Pharmacology of portal-systemic collaterals in portal hypertensive rats: role of endothelium.

The portal-systemic collateral circulation of portal hypertensive rats was studied. The collaterals were perfused through the mesenteric vein with Krebs solution, which was allowed to escape through the jugular veins. The portal-collateral resistance can be quantitated from slopes of the pressure-flow relationships. In collaterals perfused at constant flow, both norepinephrine (NE) and 5-hydroxytryptamine (5-HT) increased the perfusion pressure. Phentolamine caused surmountable antagonism of the constrictor effects of NE, suggesting an involvement of alpha-adrenoceptors. The effects of 5-HT were competitively blocked by the 5-HT2 receptor-selective antagonist ICI 169,369. Isoproterenol dilated NE-preconstricted collaterals. The effect of isoproterenol was blocked by propranolol, demonstrating that the effect was mediated by beta-adrenoceptors. Acetylcholine (ACh) dilated NE-preconstricted collaterals. The dilatation effect of ACh was absent in collaterals in which the endothelium was removed. The competitive inhibitor of the nitric oxide synthase, N omega-nitro-L-arginine (L-NNA), increased collateral resistance and prevented the ACh-induced dilatation of the collaterals. The constrictor response to L-NNA and the blockade of the ACh-induced relaxation by both L-NNA and removal of endothelium are consistent with an involvement of nitric oxide. This experimental model can thus be used to explore the pathophysiological and the pharmacological properties of the collateral venous bed in portal hypertensive states.

Animals↗
PubMed1991

Early chronic administration of propranolol reduces the severity of portal hypertension and portal-systemic shunts in conscious portal vein stenosed rats.

We investigated the effects of early chronic administration of propranolol on systemic and splanchnic hemodynamic changes, and the development of portal-systemic shunts in conscious, unrestrained, portal vein stenosed rats. Compared to rats receiving placebo, early chronic propranolol (75 mg kg-1 day-1) administration to rats begun 3 days before portal vein stenosis and then continued for 10 consecutive days, resulted in a significant decrease in both portal pressure (11.8 +/- 1.5 mmHg) and portal-systemic shunts (48 +/- 18%) which were measured 2 to 3 h after the final dose of propranolol (15.2 +/- 1.5 mmHg and 84 +/- 5%, respectively). These beneficial effects were also observed 18 to 24 h after the final dose of chronic propranolol. In rats given propranolol continuously for 5 days starting 5 days after portal vein stenosis, portal pressure (11.8 +/- 1.2 mmHg) was significantly lower than in the placebo group but portal-systemic shunts (76 +/- 14%) were not significantly different. In rats receiving a single dose of propranolol (75 mg/kg) 10 days after portal vein stenosis and measured 2 to 3 h after propranolol administration, portal pressure (12.8 +/- 1.0 mmHg) was significantly lower than in the placebo group. Portal-systemic shunts (72 +/- 17%), however, showed no significant difference from the placebo group. Similar values in portal pressure (13.3 +/- 1.2 mmHg) and portal-systemic shunts (83 +/- 21%) were also observed in rats 18 to 24 h after a single dose of propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Effects of alpha 1 and beta-adrenergic antagonists and 5-hydroxytryptamine receptor antagonist on portal-systemic collateral vascular resistance in conscious rats with portal hypertension.

In order to study the acute effects of pharmacological agents on the vascular resistance of portal-systemic collaterals, a model of total portal vein occlusion with 100% portal-systemic shunts was developed in the conscious rat. The haemodynamic effects of several vaso-active substances were evaluated in this model and compared with those obtained after saline administration. Prazosin (0.5 mg), an alpha 1-adrenergic antagonist, significantly reduced mean arterial pressure by 29%, portal pressure from 13.8 +/- 1.0(mean +/- s.e.m.) to 10.1 +/- 0.4 mmHg and portal tributary blood flow (radioactive microspheres) from 13.6 +/- 2.1 to 11.7 +/- 1.2 mL/min. It also decreased portal-systemic vascular resistance from 95 +/- 16 to 73 +/- 9 dyn s/cm5 x 10(3). Propranolol (4 mg), a beta-adrenergic antagonist, significantly reduced mean arterial pressure by 12% and portal pressure from 15.5 +/- 1.2 to 13.3 +/- 0.9 mmHg while reducing portal tributary blood flow from 14.6 +/- 1.5 to 11.0 +/- 1.7 mL/min and increasing portal systemic collateral vascular resistance from 88 +/- 7 to 103 +/- 8 dyn s/cm5 x 10(3). Ketanserin (0.25 mg/kg), a 5-hydroxytryptamine receptor antagonist, reduced portal pressure from 15.8 +/- 1.0 to 13.3 +/- 0.7 mmHg at a dose that did not alter mean arterial pressure or portal tributary blood flow. It achieved this by reducing portal-systemic collateral vascular resistance from 90 +/- 14 to 74 +/- 13 dyn s/cm5 x 10(3). Saline had no significant effect on systemic and splanchnic haemodynamics. This study shows that ketanserin decreases vascular resistance of portal-systemic collaterals while propranolol increases it. Thus, it is suggested that collateral vascular resistance is accessible to pharmacological manipulation.

Animals↗
PubMed1992

The use of quantitative scintigraphy in the measurement of portal-systemic shunting in rats.

Portal-systemic shunting was studied in 54 portal hypertensive rats both in vivo and in vitro using radioactive microspheres. The animals underwent partial portal vein ligation around needles of varying diameter to produce a wide range of shunting. Two to four weeks later, quantitative lung-liver scintigraphic and whole body images were obtained in vivo following ileocolic vein injection with 99mTc-MAA. After sacrifice, the lung and liver activities were determined by the gamma camera, a dose calibrator, and a well counter. Portal-systemic shunting ranged from 0.1-97.6%. When shunting was compared in vivo and in vitro, an excellent correlation was found (r = 0.99, p < 0.001). A subgroup of 24 animals had consecutive injections of 99mTc-MAA and 51Cr-labeled 15 microns microspheres, which, although different in size, yielded similar results (r = 0.89, p < 0.001). We conclude that in small laboratory animals a wide range of shunting can be measured accurately in vivo by quantitative scintigraphy.

Animals↗
PubMed1979

Brain proteins in experimental portal-systemic shunting.

Experimental portal-systemic shunting is accompanied by a reduction of the soluble brain proteins. Isoelectric focusing does not indicate any selective decrease of one particular protein or group of proteins. The reduction persists with sustained shunting. The interference with brain protein metabolism is compatible with a grossly normal behavior, alterness and locomotion.

Albumins↗
PubMed1991

Catecholamine concentrations in the hepatic portal system: effect of surgical stress upon portal levels.

The biological effects of a hormone are dependent on the concentration delivered to the target tissue. This is generally best reflected in the arterial concentration. However, the liver is unique in that it receives substantial additional blood flow from the portal venous system. This may be important in the case of the catecholamines, where extraction or spillover from the splanchnic circulation may occur. In this study we examined portal venous catecholamine concentrations in anesthetized, laparotomized rabbits. We compared the values with simultaneously sampled arterial levels to evaluate the effects of the splanchnic tissues upon a wide range of catecholamine concentrations delivered to the liver during a state of stress. Spillover of norepinephrine and extraction of epinephrine were observed in all rabbits. Mean (+/- SEM) arterial norepinephrine concentrations were elevated, 716 +/- 167 pg/ml (n = 11); mean portal concentrations were 178 +/- 37% higher (p less than 0.01), at 1,425 +/- 301 pg/ml, representing net spillover from splanchnic tissues. In addition, significant extraction of epinephrine was observed; arterial concentrations were 2,144 +/- 580 pg/ml (n = 11). Portal levels were 1,205 +/- 382 pg/ml, 38 +/- 7.45% lower than corresponding arterial concentrations (p less than 0.02). Furthermore, there was a concentration-dependent effect upon norepinephrine spillover; the highest arterial norepinephrine concentrations were associated with the lowest splanchnic spillover. This resulted in a negative correlation between the arterial norepinephrine levels and the percent increase from spillover into the portal vein (r = -0.81, p less than 0.003). We conclude that portal venous catecholamine concentrations are significantly different from arterial levels in anesthetized, laparotomized rabbits over a wide range of concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Long-term follow-up study of adult patients with non-cirrhotic obstruction of the portal system: comparison with cirrhotic patients.

Thirty-two patients with non-cirrhotic portal system obstruction and oesophageal varices of non-malignant etiology were recruited over 13 years. Diagnosis was based on the presence of oesophageal varices at endoscopy, minor alterations in liver function tests and liver histology, a low hepatic venous pressure gradient, and pertinent angiographic patterns. Twenty-three had portal vein thrombosis, nine had splenic vein thrombosis. Twenty-one had idiopathic portal vein obstruction, 11 had secondary obstruction. The outcome was compared with a group of 32 patients with cirrhosis and portal hypertension, matched for age, Child-Pugh class, previous history of gastrointestinal bleeding, and size of oesophageal varices. Patients with non-cirrhotic obstruction of the portal system were followed for up to 171 months (mean 94 months). During follow-up ten patients had gastrointestinal bleeding, and eight died (five of gastrointestinal bleeding). After 6 years of follow-up, the cumulative risk of gastrointestinal bleeding was 24%, the cumulative risk of death was 17%, and the cumulative risk of death from gastrointestinal bleeding was 14%. Cumulative probability of death by any cause and the probability of gastrointestinal bleeding were significantly lower in patients with non-cirrhotic obstruction of the portal system than in patients with cirrhosis comparable for liver function and portal hypertension (p = 0.04 for both). The cumulative probability of death by gastrointestinal bleeding was not significantly different. In conclusion, the prognosis for non-cirrhotic obstruction of the portal system is significantly better than for patients with cirrhosis with comparable levels of liver function impairment and severity of portal hypertension.

Adult↗
PubMed1975

Massive spontaneous portal-systemic shunting without varices.

Using umbilical vein portal phlebography, a group of patients, often with previously unsuspected liver disease or portal hypertension, have been identified with massive spontaneous portal-systemic shunts. In all cases, the collateral circulation was a single large vessel. The splenoadrenorenal, umbilical vein, or inferior mesenteric vein routes were the common pathways. These natural shunts were functional and effective in the alleviation of portal hypertension without evidence of esophageal varices or other collaterals. Portal flow was usually retrograde, perhaps contributing to the small atrophic liver seen in all patients. Six such patients were seen in the last 40 studied. This phenomenon may be more common than suspected in the cirrhotic population and account in part for differences in natural history, complications, and results of surgical therapy.

Adolescent↗
PubMed1978

Motor nerve conduction velocity in experimental portal-systemic shunting. Preliminary communication.

The influence of portal-systemic shunting on motor nerve conduction velocity (MCV) was analyzed in rats with portacaval shunts. At 3 and 8 weeks after the shunting there was a marked but transient fall in MCV. At 16 weeks the MCV had almost normalized, despite sustained portal-systemic shunting. The results favour hepatocellular failure as the more important pathophysiological mechanism in hepatic neuropathy.

Animals↗
PubMed1975

Flow and pressure characteristics of the portal system before and after splenorenal shunts.

The technique of percutaneous transhepatic portal vein cannulation provides a valuable means for determining portal pressure, direction of blood flow, and visualization of the entire portal system in the nonanesthetized patient. This technique, along with selective celiac arterial, superior mesenteric arterial, and renal venous catheterization, was used in the evaluation of a series of 17 splenorenal venous shunts [eight nonselective and nine selective (modified) distal splenorenal shunts]. As a result of these studies it is concluded that (1) prograde portal flow is maintained in the majority of patients following nonselective or selective (modified) distal splenorenal shunts; (2) bidirectional flow occurs in various branches of the portal system before and after splenorenal shunts; (3) a significant drop in portal pressure occurs following the establishment of either type of shunt; and (4) esophageal varices are decompressed by the trans-splenic route following either type of procedure used in this study.

Blood Pressure Determination↗
PubMed1977

[Clinical picture and therapy of portal-systemic encephalopathy (author's transl)].

The clinical syndrome of portal-systemic encephalopathy is caused by far advanced cirrhosis of the liver in most cases; it is characterized by increasing drowsiness, disturbances of mentation, flapping tremor and hyperreflexia. An early diagnosis can be established by testing writing and drawing abilities. Increased occurrence of spider nevi, a dry, deep red tongue, and hemorrhagic lesions of skin and mucous membranes are symptoms of incipient hepatic insufficiency. The syndrome is initiated in most cases by excessive intake of protein or alcohol, by intestinal bleeding, by diuretics, or by intercurrent infections. Therapy has to include elimination of causes, reduced intake of protein, enemas with acetate buffer solution and oral medication with lactulose, bifidum milk, and certain amino acids in order to lower hyperammoniemia; in serious cases neomycin has to be given. At the same time a normalization of fluid and electrolyte balance has to be achieved; replacement of potassium is especially important, when hypokalemia and alcalosis are present. In general prognosis of portal-systemic encephalopathy however is serious, depending primarily upon the fact, whether or not sufficient functional hepatic parenchyma is present.

Acetates↗
PubMed1975

Urinary and serum octopamine in patients with portal-systemic encephalopathy.

Urinary excretion and serum concentrations of octopamine were studied in seventeen controls, thirty-three patients with portal-systemic encephalopathy, and thirteen patients with liver disease without encephalopathy. No differences were detected between control subjects and patients without encephalopathy. Urinary excretion and serum concentrations of octopamine were significantly higher in patients with encephalopathy compared with those without encephalopathy. The presence and grade of portal-systemic encephalopathy seemed to correlate more closely with the serum-octopamine concentrations than with urinary octopamine excretion. It is postulated that octopamine may be involved in the pathogenesis of portal-systemic encephalopathy.

Adolescent↗
PubMed1992

Obliteration of portal systemic shunts as therapy for hepatic encephalopathy in patients with non-cirrhotic portal hypertension.

The effects of obliteration of portal systemic shunts (PSS) in 5 patients with non-cirrhotic hepatic encephalopathy is reported. All patients had a history of disturbance of consciousness for several years, and examinations revealed large PSS, most of which connecting the left gastric vein to the left renal vein. After the obliteration of PSS, portal vein pressure elevated, the shunt ratio of the portal blood flow decreased, the indocyanine green disappearance rate increased, and serum albumin increased. Blood ammonia (NH3) decreased significantly accompanied by disappearance of hepatic encephalopathy. This treatment may open a way to improve the quality of life in patients with large PSS without severe hepatic injury.

Aged↗
PubMed1975

Effect of hypokinesia and the combined action of gravitational load and hypokinesia on the structure of the hepatic portal system.

General hypokinesia during 1--6 weeks resulted in dilatation of the interlobular veins. sinusoids and central veins. The sequence of alterations corresponded to terms of hypokinesia. After exposure to "gravitation stress--hypokinesia for 1--6 weeks" stagnation in the portal system of the liver was less than after exposure to hypokinesia alone, but unevenness of lumens in the interlobular veins and sinusoids was more pronounced. The foci of the vessel spasm were determined. The signs of stagnation in the system of the portal vein and unevenness of the width of all the links of the portal bed were most pronounced after combination "hypokinesia for 1--6 weeks-- gravitation stress".

Adaptation, Physiological↗
PubMed1976

Angiographic documentation of systemic-portal venous shunting as a cause of a liver scan ""hot spot'' in superior vena caval obstruction.

Four patients with superior vena caval obstruction were evaluated with contrast venography and radiocolloid liver scans to investigate systemic-portal venous shunting as a cause of a liver scan "hot spot". In two of the cases a hot spot due to systemic-portal venous shunting was documented by angiography. The venous anatomy and pathophysiology related to hot spot formation on the liver scan is discussed. To develop a liver scan hot spot it appears necessary to have considerable systemic-portal venous flow through anterior parietal and periumbilical venous channels.

Angiography↗
PubMed1992

Tetrapod-like hypothalamo-hypophysial portal system in the teleost Megalops cyprinoides (Broussonet).

A tetrapod-like hypothalamo-hypophysial portal system and a persistent bucco-hypophysial canal are present in Megalops cyprinoides. The complicated loops of the primary capillary plexus are seen on the ventral side of the infundibular floor and contact the perikarya of the nucleus lateralis tuberis and the preoptico-hypothalamo-neurohypophysial-neurosecretory tract. Although the pars intermedia receives part of its vascular supply from the pars distalis, the caudal hypophysial artery directly vascularizes the neurointermedia interface and forms the plexus intermedialis. The bucco-hypophysial canal is short and narrow in the fry and fingerlings but becomes long and tortuous as the fish grows. Megapopidae seem to be closer to the polypteriformids than to the teleosts. The possession of the pituitary portal system in megalopids may be a connecting link between the polypteriformids and other advanced teleosts.

Animals↗