Human Intestinal Amino Acid Absorption and the Role of a Local (Renin)-Angiotensin System (RAS)

Aim of this trial is to investigate the expression and localisation of different amino acid transporters and their regulatory proteins derived from the regulatory proteins of the local renin angiotensin system (RAS) in the intestine. This is investigated on one hand in patients who do not take any drugs interfering with RAS. On the other hand expression analysis is done in patients taking daily RAS-active drugs, like ACE inhibitors or sartanes.

After obtaining informed consent of patients attending the hospital for clarification of gastrointestinal symptoms by gastroduodenoscopy or colonoscopy, 2 biopsies (in addition to biopsies needed for clinical diagnostics) will be taken from each duodenum, jejunum, ileum and descending colon.

Biopsies are investigated anonymously at the Institute of Physiology of the University of Zurich. The mRNA content of amino acid transporters and regulatory proteins, respectively, in the biopsies is analyzed by quantitative PCR. Transport proteins are in addition analyzed with immunohistochemistry.

Furthermore amino acid concentration in plasma and urine samples are analyzed by HPLC. From plasma and serum samples RAS parameters like renin, aldosterone, ACE and angiotensin(1-7) are measured.