Effects of propranolol on hepatic haemodynamics in the cirrhotic and non-cirrhotic rat

The effects of systemic and intraportal administration of propranolol on hepatic haemodynamics were studied in cirrhotic and non-cirrhotic rats. In the non-cirrhotic rat systemic infusion of 4 micrograms (kg body wt)-1 min-1 propranolol significantly decreased portal pressure, wedged hepatic venous pressure, portal venous flow and liver blood flow without affecting heart rate. Similar changes were observed in the cirrhotic rat following an infusion of 2 micrograms (kg body wt)-1 min-1 propranolol. Higher rates of propranolol infusion produced greater reductions in portal pressure, wedged hepatic venous pressure, portal venous flow and liver blood flow in cirrhotic and non-cirrhotic rats but these changes were accompanied by a bradycardia. The reduction in portal pressure effected by propranolol was accompanied by an increased splanchnic vascular resistance. Intraportal injection of propranolol resulted in a rapid but transient fall in portal pressure. The decrease in portal pressure was sustained if propranolol was infused intraportally. The results indicate that propranolol effects a reduction in portal pressure via a combination of increased splanchnic vascular resistance, increased hepatic arterial resistance and reduced cardiac output. The observation that propranolol can significantly reduce portal pressure without affecting heart rate may be clinically important in the long-term management of portal hypertension. Furthermore, the rapid reduction in portal pressure following intravenous administration suggests that propranolol may be of value in the acute control of variceal haemorrhage.

Effects of somatostatin and a long-acting somatostatin analogue on the prevention and treatment of experimentally induced acute pancreatitis in the rat

The effects of somatostatin (SRIF) and its long-acting analogue, SMS 201-995 on the prevention and treatment of acute pancreatitis were studied in rats. Acute pancreatitis was established by ligating the bile duct at the point of entry into the duodenum, thereby allowing reflux of bile into the pancreas. Administration of SRIF (4 micrograms kg-1 body wt IV followed by a 12 h infusion of 4 micrograms kg-1 body wt h-1) or SMS 201-995 (2 micrograms kg-1 body wt SC) at the time of bile duct ligation prevented the increase in the serum concentrations of amylase and lipase observed in control rats 12 h after bile duct ligation. Moreover, SRIF and SMS 201-995 administration prevented development of the histological changes consistent with acute pancreatitis observed in control animals. These results suggest that SRIF or SMS 201-995 may be of value in preventing acute pancreatitis following ERCP or after surgery on the pancreas. In rats with established pancreatitis, SRIF (IV bolus of 4 micrograms kg-1 body wt followed by a 24 h continuous infusion of 4 micrograms kg-1 body wt h-1) or SMS 201-995 (2 micrograms kg-1 body wt SC followed by a similar dose 12 h later): (1) significantly improved survival; (2) produced histological changes in the pancreas consistent with organization and healing; (3) prevented the accumulation of ascitic fluid; (4) reduced the serum levels of amylase and lipase. These results suggest that SRIF and SMS 201-995 may prove valuable in the treatment of established acute pancreatitis in man.

Relationship between gastric emptying of solids and gall bladder emptying in normal subjects

Very little is known about the normal temporal and quantitative relationships between gastric emptying and gall bladder emptying. Using a non-invasive double isotope technique these relationships were investigated in 22 normal healthy adults. 99Tcm EHIDA was used as the biliary tracer and 113Inm labelled bran as the gastric content tracer. Gastric emptying was monoexponential with a t1/2 of 45 +/- 3 minutes (mean +/- SEM). In 15 subjects the gall bladder emptied in relation to eating according to a double exponential function. In these subjects 15.0 +/- 1.6% of gall bladder contents emptied before gastric emptying began. They could be further divided into two clear cut types (p less than 0.001), according to the ejection fraction at 10 minutes and the t1/2 of the first exponential. Emptying of the gall bladder was faster and more of its contents were ejected in subjects with a type I response (n = 9) than in subjects with a type II response (n = 6). In the remaining seven subjects the gall bladder began to empty spontaneously, unrelated to eating. These observations suggest that gall bladder emptying: (a) may have a cephalic phase, (b) can be expressed as a double exponential function, (c) may occur unrelated to eating, (d) which occurs only in relation to eating would appear to be either fast (type I) or slow (type II).

A prospective randomised controlled clinical trial comparing somatostatin and vasopressin in controlling acute variceal haemorrhage

Twenty two patients were entered into a randomised controlled clinical trial comparing the efficacy of somatostatin and vasopressin in controlling acute variceal haemorrhage. Somatostatin was significantly more successful in controlling acute variceal haemorrhage than vasopressin (p = 0.003). Furthermore, no complications were observed during treatment with somatostatin.

A dimethylnitrosamine-induced model of cirrhosis and portal hypertension in the rat

A method of producing cirrhosis consistently in rats by the administration of dimethylnitrosamine (DMNA) is described. Two weeks following the cessation of DMNA treatment there was distortion of the lobular architecture of the liver and some focal nodule formation. This 'pre-cirrhotic' state was accompanied by portal hypertension, biochemical abnormalities and the development of ascites. The mortality 2 weeks after cessation of DMNA was 42%. Twenty-four weeks after DMNA treatment cirrhosis had developed with diffuse nodularity and fibrosis, marked portal hypertension, and accumulation of ascites. There was also a deterioration in liver function, with hypoproteinaemia and jaundice. The overall mortality 24 weeks after the cessation of DMNA treatment had risen to 52%. This model of cirrhosis in the rat may be useful in evaluating the efficacy of drugs in the long-term management of portal hypertension in man.

Circulating levels of arginine vasopressin before and during the infusion of the hormone in patients presenting with bleeding oesophageal varices

Circulating levels of antidiuretic hormone (ADH) were measured in patients presenting with bleeding oesophageal varices before and during treatment with arginine vasopressin. There was no significant difference in the circulating levels of ADH before and during treatment with arginine vasopressin in patients in which the hormone successfully controlled haemorrhage and those in which it did not. It is concluded that the failure of vasopressin to control variceal haemorrhage in approximately 40% of patients presenting for treatment cannot be attributed to higher circulating levels of the hormone in these subjects.

Isolated liver perfusion: the choice of anaesthetic

Perfused livers isolated from rats under halothane anaesthesia produced greater amounts of bile, released smaller amounts of aspartate aminotransferase, and had a much greater ability to maintain a constant concentration of glucose in perfusates than those obtained with ether or pentobarbitone. Little or no effect was shown on the ability of the liver to synthesize urea and to retain potassium within the organ. It appears, therefore,that halothane is the anaesthetic of choice when removing the liver from the laboratory rat.

2,3-O-ISOPROPYLIDENE-L-ERYTHROTETRURONIC ACID AND -L-ERYTHROSE, AND THE METHYLD-ERYTHRO- ANDD-THREO-TETROFURANOSIDES

Oxidation of 2,3-O-isopropylidene-β-L-rhamnose (I) with hypoiodite, followed by periodate cleavage of the derived aldonic acid, affords 2,3-O-isopropylidene-L-erythrotetruronic acid. Reduction of I with sodium borohydride and periodate oxidation of the resulting glycitol gives 2,3-O-isopropylidene-L-erythrose. Both products have been obtained in high yield, and are readily hydrolyzed to L-erythrotetruronic acid and L-erythrose, respectively.Methyl α- and β-D-erythro- and D-threo-tetrofuranosides have been prepared by the Fischer glycoside synthesis from D-erythrose- and D-threose-formates, respectively. A notable anomeric difference in the lead tetraacetate oxidation behavior of the methyl D-threosides has been observed, the β-anomer being more reactive than the α-anomer.

PREPARATION AND ASSAY OF D-ERYTHROSE 4-PHOSPHATE

The oxidation of D-glucose 6-phosphate by lead tetraacetate in cold acetic–propionic acid produces D-erythrose 4-phosphate contaminated with a small proportion of D-glyceraldehyde 3-phosphate. The product is a suitable substrate for certain enzymic studies, as illustrated by its use in the assay of transaldolase and transketolase. D-Erythritol 4-phosphate may readily be obtained in high yield by reducing the crude oxidation mixture with sodium borohydride. Oxidation of D-fructose 6-phosphate with 1 mole of lead tetraacetate gives chiefly D-erythrose 4-phosphate, whereas oxidation with 2 moles produces mainly D-glyceraldehyde 3-phosphate. The stability of D-erythrose 4-phosphate under a variety of conditions was also examined.

PREPARATION AND ASSAY OF D-ERYTHROSE 4-PHOSPHATE

The oxidation of D-glucose 6-phosphate by lead tetraacetate in cold acetic–propionic acid produces D-erythrose 4-phosphate contaminated with a small proportion of D-glyceraldehyde 3-phosphate. The product is a suitable substrate for certain enzymic studies, as illustrated by its use in the assay of transaldolase and transketolase. D-Erythritol 4-phosphate may readily be obtained in high yield by reducing the crude oxidation mixture with sodium borohydride. Oxidation of D-fructose 6-phosphate with 1 mole of lead tetraacetate gives chiefly D-erythrose 4-phosphate, whereas oxidation with 2 moles produces mainly D-glyceraldehyde 3-phosphate. The stability of D-erythrose 4-phosphate under a variety of conditions was also examined.