Richard B. Sewell

Hepatic Kupffer cell phagocytotic function in rats with erythrocytic-stage malaria.

Abstract Background: In the erythrocytic phase of malaria, Kupffer cells show marked hypertrophy and hyperplasia and are filled with malarial pigment. However, phagocytic function in this state has not been well characterized. The aim of the present study was to use mouse Plasmodium berghei to infect rats with malaria and study the phagocytic function and morphology of Kupffer cells.

Ageing has no effect on the volume density of hepatocytes, reticulo-endothelial cells or the extracellular space in livers of female Sprague-Dawley rats.

1. The hepatic reticuloendothelial cell population is generally assumed to increase in size, along with the liver, during ageing in rats. However, this has not been rigorously established.

Effect of 'weekend therapy' with omeprazole on basal and stimulated acid secretion and fasting plasma gastrin in duodenal ulcer patients.

The effect of intermittent dosage with omeprazole on basal and pentagastrin stimulated gastric acid secretion and fasting plasma gastrin was assessed in eight duodenal ulcer subjects who were in remission. Omeprazole (20 mg daily) was given for a three day weekend each week for two months. Twenty four hours after the first and eighth weekend, basal and peak acid output were still markedly suppressed (greater than 50%) compared with pretreatment. After the treatment free four days, however (just before the eighth weekend), peak acid output had returned to pretreatment values; basal acid output was still somewhat reduced (mean 3.6 mmol/l) but the difference from baseline was not statistically significant. Fasting plasma gastrin concentration increased slightly but significantly, from a baseline median of 17 pmol/l to 25 and 31 pmol/l respectively, 24 hours after the first and eighth weekends. All but two values (of 16) remained within the reference range. Before the fourth and eighth weekends, and again at 12 days and three months after treatment, gastrin values were not significantly different from baseline. Thus a weekend therapy regimen with this long acting antisecretory compound produces substantial acid suppression, but for only part of the week, with modest and reversible changes in fasting plasma gastrin. It should therefore be suitable for efficacy testing for prevention of recurrence of peptic ulcer or reflux oesophagitis.

Kupffer cell function during the erythocytic stage of malaria

Background and Aim:u2002 Previous studies using isolated perfused rat liver in vivo have suggested that during the erythrocytic phase of malaria infection, overall phagocytosis by Kupffer cells is enhanced. The aim of the present study was to further investigate the individual phagocytic capacity and prostaglandin E2 (PGE2) secretion of isolated Kupffer cells in vitro, and the immunohistochemical characteristics of Kupffer cells in vivo.

Ethanol-induced cell damage in cultured rat antral mucosa assessed by chromium-51 release

We have developed an in vitro method for studying ethanol-induced injury to gastric mucosa using organ culture of rat antrum. Cell damage was assessed by measurement of the release of [51Cr] sodium chromate from preloaded cells, a method adapted from a standard immunologic technique. This system provided rapid and highly reproducible quantitation of tissue injury as assessed by51Cr release into the culture medium. The threshold concentration for ethanol-induced damage was between 10 and 15% v/v, similar toin vivo thresholds observed by others.51Cr release could also be induced by very short exposure to ethanol (5–15 min), and then continued despite ethanol removal. Interestingly, after continuous ethanol exposure, a plateau of maximum51Cr release was reached 60 min after exposure to ethanol over the concentration range 20–50%, suggesting tissue adaptation to ethanol damage. This organ culture system, which allows precise control of experimental conditions, may be useful for studying mechanisms of gastric mucosal injury and protection.

Intracellular binding is an important determinant of the avid hepatic uptake of the high clearance drug omeprazole

The contribution of intracellular storage to hepatic uptake of the high clearance drug, omeprazole, was examined in the recirculating isolated perfused rat liver preparation. Following injection of [3H]omeprazole (7.5 microCi, 5 mg) into the portal vein over 1 min, livers were perfused for 5 min (N = 3) or 30 min (N = 3) and then homogenized at 4 degrees and fractionated by differential centrifugation. Radiolabelled omeprazole and metabolites were determined by scintillation counting of fractions of eluant from HPLC. Seventy per cent of drug had been taken up by the liver at 5 min and 85% at 30 min, with unchanged drug representing 43 and 7.4%, respectively, of drug taken up. At both times, 70-75% of intracellular unchanged drug and the major metabolites were located in the cytosol, and the cytosol:perfusate concentration ratio was approximately 10:1. Mitochondrial, lysosomal and microsomal fractions contained relatively little drug. Extensive cytosolic binding of omeprazole therefore contributes substantially to the initial avid hepatic first-pass uptake of this drug.

Lack of effect of omeprazole, a potent inhibitor of gastric (H++K+) ATPase, on hepatic lysosomal integrity and enzyme activity

The substituted benzimidazole, omeprazole, is a potent inhibitor of the ATP‐dependent proton pump of the parietal cell. Since there is accumulating evidence that hepatic lysosomes also possess an ATP‐dependent proton pump system to maintain internal acidification, and since antibodies to the putative lysosomal proton pump protein are immunologically similar to the parietal cell (H+ + K+) ATPase, we studied the effects in rats of six days of omeprazole treatment on hepatic lysosomal function. Omeprazole, 5 mg kg−1, a dose five times the ED50 for gastric acid secretion inhibition in rats, did not alter the activity of three representative lysosomal enzymes in liver (acid phosphatase, β‐galactosidase and N‐acetyl‐β‐glucosaminidase) nor did it alter lysosomal enzyme latency, a measure of the integrity of the lysosomal membrane. Furthermore, bile flow and the secretion of lysosomal enzymes into bile were also unaffected by omeprazole. These data indicate that in rats short‐term treatment with omeprazole, in doses that markedly inhibit gastric acid secretion, has no major biological effect on liver lysosomal integrity and lysosomal enzyme activity.

Hepatic Kupffer cell function: the efficiency of uptake and intracellular degradation of 14C-labelled mitochondria is reduced in aged rats

Uptake from the circulation and subsequent intracellular degradation of foreign and potentially harmful substances are key functions of hepatic Kupffer cells. While ageing is generally associated with decreased clearance by the reticulo-endothelial system, the effect of ageing on specific Kupffer cell functions is poorly understood. This study measured the ability of Kupffer cells of isolated perfused rat livers from young and old rats to both phagocytose and subsequently degrade exogenous radiolabelled mitochondria. Using electron microscopy and stereological techniques it was determined that there was no change in the volume density of Kupffer cells between 2 and 24 months, implying that the size of the Kupffer cell population increased (along with the total liver size) with age. However, despite this increase size there was no parallel increase in the capacity of the liver to take up or degrade radiolabelled mitochondria, implying that, in aged rats, Kupffer cell uptake and intracellular degradation was less efficient.

ETHANOL IMPAIRS BILIARY LYSOSOMAL ENZYME RELEASE IN RATS

1. The effects of ethanol on hepatic lysosomes are poorly documented. This study examined the biliary release of lysosomal enzymes, a marker of the hepatocyte‐to‐bile excretory pathway, after ethanol administration in the isolated perfused rat liver model.

High-performance liquid chromatographic method to resolve and determine lipopolysaccharide sub-groups of Escherichia coli endotoxin in isolated perfused rat liver perfusate

A high-performance liquid chromatographic method was developed for resolving heterogeneous preparations of fluorescently labelled endotoxin derived from Escherichia coli (Serotype 0111:B4) into separate lipopolysaccharide sub-groups. The endotoxin was chromatographed on an analytical gel permeation column using a mobile phase of acetonitrile (20%, v/v) and 100 mM phosphate buffer (pH 7.75). Four fluorescent peaks were resolved, representing sub-groups of markedly different molecular sizes. Three of the four sub-groups contained the core polysaccharide 2-keto-3-deoxyoctonate, confirming that they contained lipopolysaccharide. Fluorescein isothiocyanate (FITC)-labelled endotoxins derived from Vibrio cholerae and Salmonella minnesota chromatographed using the same system eluted with distinctly different patterns of peaks from each other and from E. coli. Extraction of E. coli FITC-endotoxin from a buffer solution using a phenol-diethyl ether method and subsequent chromatography allowed the determination of three of the four fluorescent sub-groups over the concentration range 1-15 micrograms/ml.