|Ulrike Lodemann :
Studies on transport physiology in isolated rumen epithelium of sheep: effects of an increased osmotic pressure and feeding conditions
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.
Download the whole PhDthesis as a zip-tar file or as zip-File For download in PDF format click the chapter title
For download in PDF format click the chapter titleTitelblatt, Inhaltsverzeichnis, Lebenslauf
|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|
|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|
||| DARWIN|| Digitale Dissertationen || Dissertation|| German Version|| FU Berlin|| Seitenanfang |||
|Fragen und Kommentare an:|
© Freie Universität Berlin 1999