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FU Berlin
Digitale Dissertation

Ulrike Lodemann :
Studies on transport physiology in isolated rumen epithelium of sheep: effects of an increased osmotic pressure and feeding conditions
Transportphysiologische Untersuchungen am isolierten Pansenepithel des Schafes: Auswirkungen eines erhöhten osmotischen Druckes bei unterschiedlicher Fütterung

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|Abstract| |Table of Contents| |More Information|


The intention of this study was to test the possible dietary dependent effect of luminal osmotic pressure on characteristics of the ruminal epithelium.
Sheep were kept under different dietary trials for at least three weeks: (1) hay ad libitum, (2)600 g concentrate/d, (3) 1200 g concentrate/d and (4) 1800 g concentrate/d. In addition to the concentrate, sheep were offered hay ad libitum. The experiments were conducted in vitro with isolated ruminal epithelial tissues using conventional Ussing chamber technique. In these experiments, luminal osmolarity was adjusted by mannitol to 300 mosmol/l in the control group and to 375 or 450 mosmol/l in the experimental groups.
1. Concentrate feeding led to an increase of net Na transport (Jnet Na); this is due to the stimulation of the mucosal to serosal sodium transport (Jms Na) and most probably due to an increase in the apical Na/H exchanger activity.
2. Under all dietary trials, increasing the luminal osmolarity resulted in an elevation of the tissue conductance (Gt). This increase in conductance was lowest at higher concentrate feeding. This modification of Gt could be attributed to paracellular effects under hay and 600 g concentrate dietary trials and probably to transcellular effects under higher concentrate dietary trials. Thus, the osmotic resistance of the epithelium seems to increase with higher concentrate intake.
3. Increasing luminal osmotic pressure resulted in a reduction of net Na transport, this reduction was most pronounced at higher concentrate intake.
4. Hay and 600 g concentrate/d feeding led to a stimulation of the serosal to mucosal Na flux (Jsm Na); however, higher concentrate intake (1200 and 1800 g concentrate/d) did not show any effect.
5. At higher concentrate intake (1200 and 1800 g concentrate/d) increasing luminal osmotic pressure resulted in a reduction of the mucosal to serosal Na flux. This is probably due to the inhibition of the Na/H exchanger activity.
6. The results are discussed regarding their possible practical meaning.

Table of Contents

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Titelblatt, Inhaltsverzeichnis, Lebenslauf
1. Einleitung
2. Literatur
3. Material und Methoden
4. Ergebnisse
5. Diskussion
6. Zusammenfassung / Summary
7. Anhang

More Information:

Online available: http://www.diss.fu-berlin.de/2002/298/indexe.html
Language of PhDThesis: german
Keywords: Sheep, Rumen, Epithelium, Osmolarity, Osmotic Pressure, Physiology, Electrophysiology, Ion Transport, Sodium, Adaptation, Concentrates, Feeding, In Vitro, Absorption, Electrical Conductance, Ruminants, Rumen Epithelium
DNB-Sachgruppe: 34 Veterinärmedizin
Date of disputation: 23-Nov-2001
PhDThesis from: Fachbereich Veterinärmedizin, Freie Universität Berlin
First Referee: Univ.-Prof. Dr. Holger Martens
Second Referee: Prof. Dr. Klaus Männer
Third Referee: Univ.-Prof. Dr. Johanna Plendl
Contact (Advisor): lodemann@zedat.fu-berlin.de
Date created:22-Dec-2002
Date available:12-Aug-2003


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