Dipeptide metabolism in the isolated perfused rat small intestine.
The purpose of the present study was to investigate the utilisation of vascularly administered leucyl-leucine (Leu-Leu), alanyl-glutamine (Ala-Gln) and glycyl-glutamine (Gly-Gln) by the isolated vascularly perfused rat small intestine. Fractional extraction rates were 49%, 35.5%, and 12% for Leu-Leu, Ala-Gln, and Gly-Gln (0.15mM) corresponding to a net uptake of -63.5, -31.5, and -17 nmol/min/g wet weight. Nitrogen metabolism in terms of glutamine uptake and release of alanine and ammonia was not different when perfusion with dipeptides or with free amino-acids were compared. No soluble dipeptidase activity was released into the plasma- and cell-free synthetic vascular perfusate. No dipeptide could be recovered from the luminal perfusate. Considering the high fractional extraction rate for Leu-Leu, it is conceivable that dipeptide assimilation may occur also in extramucosal gut tissue. Although dipeptide transport cannot be excluded, dipeptide assimilation in small intestine may involve membrane bound peptidase(s), as in liver.
Plauth
M
M
Eberhard-Karls-Universität, Medizinische Klinik und Poliklinik, Abteilung Innere Medizin I, D-7400 Tübingen, Germany.
Kremer
I
I
Raible
A
A
Stehle
P
P
Fürst
P
P
Hartmann
F
F