Tripeptide transport in rat lung.
Transport of L-alanyl-D-phenylalanyl-L-alanine was investigated with an in situ vascular perfusion preparation of rat lung and brush border membrane vesicles prepared from type II pneumocytes. In the perfused lung 1 mM tripeptide was transported intact from the alveolar lumen to the vascular perfusate at a mean rate of 25.1 +/- 1.29 (3) nmol/min per g dry weight. D-Phenylalanine also appeared in the vascular perfusate at a rate of 21.9 +/- 1.74 (3) nmol/min per g dry weight indicating that 47% of the absorbed tripeptide was split during passage across the epithelial layer. No dipeptide could be detected in the vascular effluent during perfusions with tripeptide. Rapid L-alanyl-D-phenylalanyl-L-alanine uptake occurred with fresh apical membrane vesicles prepared from type II pneumocytes and this was abolished by treatment with 0.1% triton. The related tripeptide, D-alanyl-L-phenylalanyl-D-alanine, was taken up significantly more slowly by the vesicles. D-phenylalanyl-L-alanine and D-phenylalanyl-D-alanine, were also studied with the vascularly perfused preparation; the mixed dipeptide appeared in the vascular perfusate significantly faster than L-alanyl-D-phenylalanyl-L-alanine whereas D-phenylalanyl-D-alanine appeared more slowly and was not hydrolysed.
Helliwell
P A
PA
Department of Biology, University of York, UK.
Meredith
D
D
Boyd
C A
CA
Bronk
J R
JR
Lister
N
N
Bailey
P D
PD
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D008168:Lung / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008871:Microvilli / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D010455:Peptides; D010649:Phenylalanine