Transport of glycyl-L-proline in intestinal brush-border membrane vesicles of the suckling rat: characteristics and maturation.
Transport of the dipeptide glycine-L-proline (Gly-L-Pro) in the developing intestine of suckling rats and its subsequent maturation in adult rats was examined using the brush-border membrane vesicles (BBMV) technique. Uptake of Gly-L-Pro by BBMV was mainly the result of transport into the intravesicular space with little binding to membrane surfaces. Transport of Gly-L-Pro in BBMV of suckling rats was: (1) Na+ independent; (2) pH dependent with maximum uptake at an incubation buffer pH of 5.0; (3) saturable as a function of concentration (apparent Km = 21.5 +/- 7.9 mM, Vmax = 8.6 +/- 1.5 nmol/mg protein per 10 s); (4) inhibited by other di- and tripeptides; and (5) stimulated and inhibited by inducing a negative and positive intravesicular membrane electrical potential, respectively. Similarly, transport of Gly-L-Pro in intestinal BBMV of adult rats was saturable as a function of concentration (apparent Km = 17.4 +/- 8.6 mM, Vmax = 9.1 +/- 2.1 nmol/mg protein per 10 s) and was stimulated and inhibited by inducing a relatively negative and positive intravesicular membrane potential, respectively. No difference in the transport kinetic parameters of Gly-L-Pro was observed in suckling and adult rats, indicating a similar activity (and/or number) and affinity of the transport carrier in the two age groups. These results demonstrate that the transport of Gly-L-Pro is by a carrier-mediated process which is fully developed at the suckling period. Furthermore, the process is H+-dependent but not Na+-dependent, electrogenic and most probably occurs by a Gly-L-Pro/H+ cotransport mechanism.
Said
H M
HM
Department of Pediatric Gastroenterology, Vanderbilt University School of Medicine, Nashville, TN 37232.
Ghishan
F K
FK
Redha
R
R
D000818:Animals; D000833:Animals, Suckling / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D004151:Dipeptides / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000254:growth & development*; D007700:Kinetics; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
D004151:Dipeptides; D014634:Valinomycin; C015248:glycylproline; D012964:Sodium; D011188:Potassium; D005998:Glycine