ISSN:
1573-2568
Schlagwort(e):
CYCLOSPORIN A
;
CHOLESTASIS
;
TIGHT JUNCTION
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Abstract The immunosuppressive agent cyclosporin A (CsA)is known to cause cholestasis. Transcellular andparacellular transport of macromolecules contribute,albeit to a minor extent, to bile formation, but little is known about the effects of CsA on thesepathways. The aims of this study were to investigate theinfluence of CsA on tight junction (paracellular)permeability and on transcytotic vesicular pathways labeled with horseradish peroxidase (HRP) inperfused rat liver. Livers from male Sprague-Dawley ratswere perfused with Krebs-Henseleit buffer (albumin 1%,RBC 20%, and amino acid mixture). Taurodehydrocholate (1 μM/min) was coinfused into the portalvein; 1 μg/ml of CsA, dissolved in Cremophor-EL (CsAlivers), or the vehicle alone (CEL livers), was added tothe medium. Tight junction permeability was assessed by administering HRP (25 mg) as a short pulseto perfused rat livers, operating under single-passconditions. Under such conditions, HRP output into thebile shows two components: an initial peak atapproximately 3-5 min, corresponding to paracellular transferacross tight junctions, and a second peak atapproximately 15 min, corresponding to vesiculartransport. Furthermore, we assessed the vesiculartransport pathway by examining HRPlabeled vesicles in theperisinusoidal (PS) and pericanalicular (PC) areas usingultrastructural morphometric analysis. To analyze HRP inhepatocytes and to study rapid and late transcytotic vesicular pathways, a 1-min pulseof a high dose of HRP (500 and 200 mg, respectively) wasgiven. Two and 18 min after single-pass perfusion thelivers were fixed with 2.5% glutaraldehyde- 0.8% paraformaldehyde in 0.1 mM cacodylatebuffer, pH 7.8. The total pericanalicular area, theHRP-containing structures, were quantifiedmorphometrically in liver samples. At concentrations of1.2 μg/ml, CsA produced a twofold increase in theparacellular transfer of HRP to bile. The areas underthe second peak (transcellular vesicular pathway) of thebiliary HRP secretion curve were similar in CEL- and CsA-treated livers. Morphometric analysisconfirmed that CsA treatment did not affect thepercentage area of HRP-labeled vesicles in either thepericanalicular or in the perisinusoidal area at 2 min(rapid pathway) and 18 min (late pathway). Theseresults indicate that CsA increases tight junctionalpermeability whereas it does not inhibit rapid or latetranscytotic vesicle pathways.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1018834723417
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