First-pass lung uptake and pulmonary clearance of propofol: assessment with a recirculatory indocyanine green pharmacokinetic model

BACKGROUND: The principal site for elimination of propofol is the liver. The clearance of propofol exceeds hepatic blood flow; therefore, extrahepatic clearance is thought to contribute to its elimination. This study examined the pulmonary kinetics of propofol using part of an indocyanine green (ICG) recirculatory model. METHODS: Ten sheep, immobilized in a hammock, received injections of propofol (4 mg/kg) and ICG (25 mg) via two semipermanent catheters in the right internal jugular vein. Arterial blood samples were obtained from the carotid artery. The ICG injection was given for measurement of intravascular recirculatory parameters and determination of differences in propofol and ICG concentration-time profiles. No other medication was given during the experiment, and the sheep were not intubated. The arterial concentration-time curves of ICG were analyzed with a recirculatory model. The pulmonary uptake and elimination of propofol was analyzed with the central part of that model extended with a pulmonary tissue compartment allowing elimination from that compartment. RESULTS: During the experiment, cardiac output was 3.90+/-0.72 l/min (mean +/- SD). The blood volume in heart and lungs, measured with ICG, was 0.66+/-0.07 l. A pulmonary tissue compartment of 0.47+/-0.16 l was found for propofol. The pulmonary first-pass elimination of propofol was 1.14+/-0.23 l/min. Thirty percent of the dose was eliminated during the first pass through the lungs. CONCLUSIONS: Recirculatory modeling of ICG allows modeling of the first-pass pulmonary kinetics of propofol concurrently. Propofol undergoes extensive uptake and first-pass elimination in the lungs.     

The influence of Helicobacter pylori on oesophageal acid exposure in GERD during acid suppressive therapy

BACKGROUND: Helicobacter pylori exaggerates the effect of acid suppressive drugs on intragastric pH. It is unknown whether this is relevant for the treatment of GERD. AIM: To compare oesophageal acid exposure and symptoms in H. pylori-negative and H. pylori-positive GERD patients during low and profound acid suppression. METHODS: Barrett's oesophagus patients with gastro- oesophageal acid reflux were studied by 24-h oesophageal pH-metry at baseline and during randomized treatment with omeprazole 40 mg b.d. or ranitidine 150 mg b.d. H. pylori status was determined by a serum IgG ELISA. Symptoms were scored on a four-graded scale. RESULTS: Of 58 patients, 26 (14 H. pylori-negative, 12 H. pylori-positive) were randomized to omeprazole, 32 (16 H. pylori-negative, 16 H. pylori-positive) to ranitidine. At baseline, oesophageal acid exposure and symptoms did not differ between H. pylori-negative and H. pylori-positive: mean time proportion pH < 4 per 24 h was 16.1% (95% CI 11.5-23.2) in H. pylori-negative, and 15.8% (11.3-21.4) in H. pylori-positive patients. Omeprazole treatment resulted in a decrease of acid reflux per 24 h from 23.4% (7.9-39.3) to 0.0% (0.0-2.9) in H. pylori-negative, and from 17.3% (8.9-38.8) to 0.1% (0.0-1.7) in H. pylori-positive patients; ranitidine resulted in a decrease from 14.4% (10.5-18.5) to 9.3% (5.6-12.8) in H. pylori-negative, and from 15.1% (9.8-21.0) to 9.0% (3.1-20.1) in H. pylori-positive patients, the difference between H. pylori-negative and H. pylori-positive patients being N.S. There was no significant difference between H. pylori-negative and H. pylori-positive patients with respect to erect and supine acid reflux, or symptom scores in both treatment groups. CONCLUSIONS: H. pylori infection does not influence oesophageal acid reflux and symptoms in patients with Barrett's oesophagus, either at baseline or during low as well as profound acid suppressive therapy. We conclude that the dose of acid suppression does not have to be titrated upon H. pylori status in GERD.     

Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols

In order to study the biological activities of tea preparations and purified tea polyphenols, their growth inhibitory effects were investigated using four human cancer cell lines. Growth inhibition was measured by [3H]thymidine incorporation after 48 h of treatment. The green tea catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)- epigallocatechin (EGC) displayed strong growth inhibitory effects against lung tumor cell lines H661 and H1299, with estimated IC50 values of 22 microM, but were less effective against lung cancer cell line H441 and colon cancer cell line HT-29 with IC50 values 2- to 3- fold higher. (-)-Epicatechin-3-gallate, had lower activities, and (-)- epicatechin was even less effective. Preparations of green tea polyphenols and theaflavins had higher activities than extracts of green tea and decaffeinated green tea. The results suggest that the growth inhibitory activity of tea extracts is caused by the activities of different tea polyphenols. Exposure of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the induction of apoptosis as determined by an annexin V apoptosis assay, showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM of these compounds, the apoptosis indices were 82, 76 and 78%, respectively. Incubation of H661 cells with EGCG also induced a dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused apoptosis in a manner similar to that caused by EGCG. The EGCG-induced apoptosis in H661 cells was completely inhibited by exogenously added catalase (50 units/ml). These results suggest that tea polyphenol-induced production of H2O2 may mediate apoptosis and that this may contribute to the growth inhibitory activities of tea polyphenols in vitro.