Increased formation of S-nitrothiols and nitrotyrosine in cirrhotic rats during endotoxemia.

Plasma S-nitrosothiols are believed to function as a circulating form of nitric oxide that affects both vascular function and platelet aggregation. However, the formation of circulating S-nitrosothiols in relation to acute and chronic disease is largely unknown. Plasma S-nitrosothiols were measured by chemiluminescence in rats with biliary cirrhosis or controls, and the effect of lipopolysaccharide (LPS) on their formation was determined. Plasma S-nitrosothiols were increased in rats with cirrhosis (206 +/- 59 nM) compared to controls (51 +/- 6 nM, p <.001). Two hours following injection of LPS (0.5 mg/kg) plasma S-nitrosothiols increased to 108 +/- 23 nM in controls (p <.01) and to 1335 +/- 423 nM in cirrhotic rats (p <.001). The plasma clearance and half-life of S-nitrosoalbumin, the predominant circulating S-nitrosothiol, were similar in control and cirrhotic rats, confirming that the increased plasma concentrations were due to increased synthesis. Because reactive nitrogen species, such as peroxynitrite, may cause the formation of S-nitrosothiols in vivo, we determined the levels of nitrotyrosine by gas chromatography/mass spectrometry as an index for these nitrating and nitrosating radicals. Hepatic nitrotyrosine levels were increased at 7.0 +/- 1.2 ng/mg in cirrhotic rats compared to controls (2.0 +/- 0.2 ng/mg, p <.01). Hepatic nitrotyrosine levels increased by 2.3-fold and 1.5-fold in control and cirrhotic rats, respectively, at 2 h following injection of LPS (p <.01). Strong positive staining for nitrotyrosine was shown by immunohistochemistry in all the livers of the rats with cirrhosis. We conclude that there is increased formation of S-nitrosothiols and nitrotyrosine in biliary cirrhosis, and this is markedly upregulated during endotoxemia.

The organ extraction and splanchnic haemodynamic effects of octreotide in cirrhotic patients.

BACKGROUND: Intravenous octreotide is an established treatment of oesophageal variceal haemorrhage in the cirrhotic patient. AIM: To examine the organ extraction and splanchnic haemodynamic effects of octreotide in cirrhotic patients with portal hypertension. METHODS: Thirteen patients with cirrhosis had hepatic venous catheterization performed. Hepatic venous pressure gradient (HVPG), indocyanine green (ICG) clearance and hepatic blood flow (HBF) were determined in the basal state and during 60 min of octreotide infusion by bolus injection (0.75 microg/kg) followed by continuous infusion of 0.75 microg/kg x h. Blood samples were simultaneously drawn from the femoral artery and the hepatic and renal veins. RESULTS: The extraction fraction of octreotide in the liver was 0.05 (-0.01 - 0.14) (median (interquartile range)) and in the kidneys 0.16 (-0.06 - 0.35). The extraction fraction ratio (E(liver)/E(kidney)) was 0.69 (-0.20 - 1.06). Hepatic clearance was 47 mL/min (3-88) (n = 11). No correlations were found between liver biochemistry or galactose elimination capacity (GEC; a metabolic measure of liver function) and renal extraction fraction or liver clearance. Octreotide had no effect on HVPG or wedged hepatic venous pressure although free hepatic venous pressure increased during octreotide infusion: 6 mmHg (5-9) vs. 7 mmHg (6-10) (P = 0.02). No effect on HBF was observed while ICG clearance decreased significantly. CONCLUSIONS: Octreotide is extracted in cirrhotic patients by both the liver and the kidney, the latter being the most important organ of elimination. Octreotide decreases liver metabolic activity determined by the ICG clearance technique, but no significant effects of octreotide on HVPG or HBF could be demonstrated.

Differential response to gefitinib of cells expressing normal EGFR and the mutant EGFRvIII.

Epidermal growth factor receptor (EGFR) is frequently amplified and/or mutated in a number of human tumours and abnormal signalling from this receptor is believed to contribute to the malignant phenotype seen in these tumours. Gefitinib is a small molecule inhibitor that specifically binds and inhibits the EGFR tyrosine kinase and has been shown to inhibit the growth, proliferation, survival and invasion of a range of tumour cells overexpressing EGFR. However, clinical response to gefitinib has failed to correlate with EGFR levels and activity, indicating that other molecular mechanisms such as downstream signalling and mutations could be of importance in predicting clinical response. We therefore investigated the effect of the specific EGFR inhibitor gefitinib on the phosphorylation level, signalling and growth of cells expressing the naturally occurring constitutively active EGFR variant EGFRvIII, a low nontransforming level of EGFR and a high transforming level of EGFR. Results show that levels of gefitinib sufficient to suppress EGFR phosphorylations, EGFR-mediated proliferation and EGFR-mediated anchorage-independent growth are not sufficient to inhibit these features in cells expressing EGFRvIII. Furthermore, the data indicate that long-term exposure of EGFRvIII-expressing cells to low concentrations of gefitinib (0.01-0.1 microM) result in increased phosphotyrosine load of the receptor, increased signalling to ERK and stimulation of proliferation and anchorage-independent growth, presumably by inducing EGFRvIII dimerisation. Higher concentrations of gefitinib (1-2 microM), on the other hand, significantly decreased EGFRvIII phosphotyrosine load, EGFRvIII-mediated proliferation and anchorage-independent growth. Further studies are needed to investigate the implications of these important findings in the clinical setting.

The pharmacokinetics of octreotide in cirrhosis and in healthy man.

BACKGROUND/AIM: The aim of the study was to evaluate the pharmacokinetics of octreotide in patients with cirrhosis compared to healthy volunteers. METHODS: Seventeen patients with cirrhosis and nine normals received an intravenous bolus of octreotide (0.75 microgram/kg), followed by a continuous infusion of 0.75 microgram.kg-1.h-1 for 12 h. Eight patients were decompensated with ascites, while nine were without signs of decompensation. Serum octreotide levels were followed by blood sampling during the infusion period and for 24 h afterwards. RESULTS: The average clearance (+/-SEM) was 151 +/- 15 ml/min in normals compared to 102 +/- 9 (p < 0.05) and 105 +/- 9 (p < 0.05) in patients with compensated and decompensated cirrhosis, respectively. The average area under the serum octreotide curve was significantly increased by 53% (p < 0.05) in decompensated and 46% (p < 0.05) in compensated cirrhosis compared to healthy volunteers, while no difference was observed between the groups with cirrhosis. This difference was also reflected by an increased maximum serum concentration during the infusion period of 9797 +/- 580 ng/l in the patients with cirrhosis compared to 7081 +/- 547 ng/l (p = 0.006) in normals. The serum half-life for the beta-phase (T1/2 beta) was 165 +/- 26 min in normals, 200 +/- 21 min in the compensated and 216 +/- 26 min in the decompensated group (NS). The volume of distribution (Vd beta) showed no difference between the three groups. Because of the slow equilibration between plasma and ascitic fluid in decompensated cirrhosis, the calculated clearance may have been overestimated and T1/2 beta and Vd beta underestimated in these patients. CONCLUSIONS: The present study demonstrates that the pharmacokinetics of octreotide in cirrhosis is substantially different from that found in normals.

The insulin-like growth factor binding protein 3 ternary complex is reduced in cirrhosis.

BACKGROUND/AIMS: In healthy adults, serum insulin-like growth factor I (IGF-I), IGF binding protein 3 (IGFBP-3) and acid labile subunit (ALS) form a 150-kDa ternary complex under the control of growth hormone (GH). Approximately 80-90% of circulating IGF-I is bound to the ternary complex. In cirrhosis the GH/IGF axis is severely disturbed and the individual components of the ternary complex are reduced. However, the degree of ternary complex formation in cirrhosis has not previously been described. METHODS: Serum IGF-I, IGFBP-3, ALS, the 150-kDa ternary complex and IGFBP-3 proteolysis were all measured in six compensated and six decompensated cirrhotic patients and compared to six healthy controls. RESULTS: Patients with compensated cirrhosis had decreased levels of IGF-I (55%), IGFBP-3 (64%) and ALS (53%), and in the decompensated patients these levels were decreased even further: IGF-I (32%), IGFBP-3 (37%) and ALS (27%) compared to healthy controls. The levels of the ternary complex followed this pattern, with low levels seen in the compensated patients (66%) and a further reduction in the decompensated patients (27%). Ternary complex levels correlated negatively with the Child-Pugh score. No increase in IGFBP-3 proteolysis was found in cirrhotic patients compared to healthy controls. CONCLUSION: Cirrhosis is associated with reduced levels of the 150-kDa ternary IGFBP-3 complex correlating with the degree of liver disease.

Effects of octreotide on serum insulin-like growth factor I and insulin-like growth factor binding proteins in patients with cirrhosis.

Hyperinsulinaemia and reduced insulin sensitivity are common features in patients with cirrhosis. Octreotide, a long-acting somatostatin analogue, is used in cirrhotic patients in the treatment of bleeding oesophageal varices. Octreotide has potent effects on the growth hormone (GH)/insulin-like growth factor I (IGF-I) axis in healthy subjects. but the effects on the GH/IGF-I axis in patients with cirrhosis have been described only briefly. The effects of a 12 h infusion of octreotide (bolus 0.75 microg/kg followed by 0.75 microg/kg/h) in 25 subjects (normals n=9, compensated cirrhotics n=8, decompensated cirrhotics n=8) were compared with those in placebo-treated controls (n=19) during fasting conditions. IGF-I, free IGF-I, IGF binding proteins (IGFBPs), insulin, C-peptide, GH and glucose were measured. Insulin resistance was calculated using the HOMA method. Octreotide reduced levels of total IGF-I in patients with compensated cirrhosis (p=0.03) and free IGF-I in decompensated cirrhosis (p<0.01). Insulin resistance was significantly reduced in normal subjects. whereas the reduction in insulin resistance did not reach statistical significance in patients with cirrhosis. In normal subjects, octreotide increased the IGFBP-1 area under curve threefold (p<0.01) and decreased IGFBP-3 levels (p<0.01), but these effects were blunted in the cirrhotic patients. Similarly, the reduction of insulin and C-peptide was blunted in the cirrhotic patients, whereas a significant reduction in GH was demonstrated in all groups. The effects of octreotide on the GH/IGF-I axis are mitigated in patients with cirrhosis and this may be a reflection of relative hyperinsulinaemia during octreotide treatment in these patients.

Protein C activation during the initial phase of experimental acute pancreatitis in the rabbit.

BACKGROUND: Disturbances of coagulation and fibrinolysis are well-known systemic effects of acute necrotising pancreatitis (ANP). The purpose of this experimental study was to evaluate the initial events in the haemostatic activation during ANP in an animal model with relevance to the human situation. METHODS: ANP was introduced in 7 rabbits by infusion of chenodeoxycholic acid in the pancreatic duct. Seven rabbits served as sham-operated controls. Serial measurements of coagulation variables (prothrombin time, activated partial thromboplastin time, FVII activity, fibrinogen, tissue factor activity), anticoagulant proteins (protein C, antithrombin) and fibrinolytic factors (tissue plasminogen activator, plasminogen activator inhibitor-1) were performed for 5 h. RESULTS: ANP was confirmed by elevated serum amylase, development of ascites, and histological changes of the pancreas. A moderate activation of the coagulation system was found in both study groups. A significant decrease in protein C concentration from 1 h after the induction of ANP was found, whereas the response of antithrombin and the inhibition of the fibrinolytic system were similar in the 2 study groups. Microthrombosis of the lungs or kidneys was found in 2 rabbits with ANP. CONCLUSION: An immediate activation of protein C is a specific characteristic of the haemostatic activation in ANP in rabbits. This activation has not been described previously and the possible therapeutic implications ought to be studied.

Effects of a long-acting formulation of octreotide on renal function and renal sodium handling in cirrhotic patients with portal hypertension: a randomized, double-blind, controlled trial.

Octreotide seems to have a beneficial effect on variceal bleeding, and long-term administration for the prevention of rebleeding is currently being evaluated. Experimental studies have suggested a beneficial effect of chronic octreotide treatment on renal function, while clinical studies have shown variable effects. Twenty-five cirrhotic patients with portal hypertension were randomized in a double-blind design to placebo or a single subcutaneous dose of a long-acting formulation of octreotide (octreotide-LAR) (20 mg). Renal function tests were performed before dosing and repeated after 30 days. The patients were in sodium steady state at the time of study. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by a constant infusion clearance technique. Renal sodium handling was determined by lithium and sodium clearance measurements. Therapeutic serum levels of octreotide along with a reduction of insulin-like growth factor I (IGF-I) (P <.01) and an increase of IGF binding protein 1 (P <.05) were demonstrated. No effect of octreotide was observed on GFR, ERPF, or filtration fraction (GFR/ERPF). Changes in clearance and extraction fraction of sodium and lithium during octreotide treatment were not significantly different from those of placebo. In addition, no changes in free water clearance, urinary flow rate, or 24-hour Na excretion were demonstrated. A significant increase of mean arterial pressure (+5 mm Hg; P <.01) was observed after treatment with octreotide-LAR. It is concluded that in spite of increased arterial pressure, octreotide-LAR has no significant effect on renal hemodynamics and tubular function in clinically stable cirrhotic patients with portal hypertension.