Cellular uptake of fluvastatin, an inhibitor of HMG-CoA reductase, by rat cultured hepatocytes and human aortic endothelial cells.

AIMS: To clarify the mechanism for cellular uptake of fluvastatin (FV) into rat primary cultured hepatocytes and human aortic endothelial cells (HAEC). METHODS: Rat primary cultured hepatocytes and Endocell-AO as normal human aortic endothelial cells were used. Effects of incubation time, concentration- and temperature-dependency on cellular FV uptake were investigated after incubation with [14C]-FV and its enantiomers, (+)-FV and (-)-FV. Rat primary cultured hepatocytes were washed with either Na+-containing buffer or Na+-free buffer and incubated with metabolic inhibitors or bile acids. Intracellular radioactivity was measured by liquid scintillation counting. The determination of intracellular unchanged FV and its enantiomers was carried out by stereospecific h.p.l.c. RESULTS: In rat cultured hepatocytes, concentration- and temperature-dependent saturable uptake of [14C]-FV was observed (Km=37.6 microm, V max=869 pmol (mg protein)-1 min-1 ), suggesting a specific uptake mechanism. The uptake of each enantiomer also showed a specific uptake mechanism as observed for the racemate with no difference between enantiomers; (+)-FV, Km=38.5 microm, V max=611 pmol (mg protein)-1 min-1, (-)-FV, Km=41.5 microm, V max=646 pmol (mg protein)-1 min-1. In the presence of cholate and taurocholate, the uptake of FV was inhibited by 39-46%. Pravastatin inhibited FV uptake by 29%. In the absence of Na+, the uptake of FV was markedly inhibited 91-96% by bile acid. The uptake of FV into HAEC at 37 degrees C and 4 degrees C increased with the concentration of FV, but no saturable uptake was observed. CONCLUSIONS: FV transport system may be, at least in part, Na+- and ATP-dependent, and may have some features in common with the bile acid transport system and the organic anion transport system. Since saturable uptake was not observed in HAEC, FV appears to be taken up into these cells mainly via nonspecific simple diffusion.

Dose-dependent effects of PSC 833 on its tissue distribution and on the biliary excretion of endogenous substrates in rats.

PSC 833, a nonimmunosuppressive cyclosporin, is a potent inhibitor of the efflux of antitumor drugs mediated by P-glycoprotein and thus has been introduced in clinical trials as an agent to overcome multidrug resistance. The purpose of this study was to evaluate the dose-dependent pharmacokinetics of PSC 833 and its effects on the biliary excretion of endogenous substrates in rats. The major elimination route for PSC 833 is metabolism, followed by excretion into bile. The biliary clearance of PSC 833 was reduced in a dose-dependent manner, whereas no urinary excretion of PSC 833 was detectable. The tissue/blood concentration ratios for PSC 833 in the liver, kidney, intestine, and spleen were reduced in a dose-dependent manner, suggesting the presence of a saturable uptake process and/or saturable binding in these tissues. The dose-dependent increase in the tissue/blood concentration ratio in the brain suggests the presence of efflux transporters on the blood-brain barrier. PSC 833 reduced the bile flow rate by decreasing the biliary excretion of bile acids and reduced and oxidized glutathione, in a dose-dependent manner. The mechanism for the dose-dependent disposition of PSC 833 and its effects on the biliary excretion of endogenous substrates could be related to interactions with transporters.

The first reported case of intestinal spirochaetosis in Japan.

A 65-year-old Japanese male consulted Ozuchi Prefectural Hospital (Iwate, Japan) on 19 January 1994 complaining of weight loss. Cecal mucosal biopsy material, which was stained with hematoxylin-eosin revealed a thick, basophilic fuzzy fringe covering the surface epithelium. Transmission and scanning electron microscopy observations demonstrated the presence of slightly wavy spirochaetes with tapered ends, which were attached to the surface epithelium of the colonic mucosa via one of these ends. The patient did not display any clinical symptoms of inflammatory bowel disease, and laboratory tests eliminated an immunodeficiency condition. Thus, in the present case, the intestinal spirochaetes appear to be harmless commensals. This paper presents the first reported case of intestinal spirochaetosis in Japan.

Hyperplastic (metaplastic) polyposis of the colorectum associated with adenomas and an adenocarcinoma.

Hyperplastic (metaplastic) polyposis associated with adenoma and adenocarcinoma of the colorectum is rare. We describe a 55-year-old man with hyperplastic polyposis associated with multiple adenomas and an adenocarcinoma who underwent total colectomy. We found at least 200 polyps in the surgical specimen. Nearly all of the polyps were hyperplastic, and some were adenomas. Furthermore, some hyperplastic polyps had adenomatous areas. This indicates the transformational sequence of a hyperplastic polyp to adenoma to adenocarcinoma.