Absorption kinetics of beta-alanine as model compound in rat small intestine.
Contradictory results have been reported on intestinal beta-alanine absorption, although a generalized view is that it could be a passive, nonmediated process. Since previous data from our laboratory suggested that some competition arises between intestinal absorption of the gamma-amino acidic drug baclofen and beta-alanine, a rat jejunum in situ study was undertaken in order to gain insight into the mechanism of beta-alanine absorption. Perfusion solutions with initial beta-alanine concentrations ranging from 0.3 to 56 mM were used. The beta-alanine absorption was clearly identified as a saturable process which obeys Michaelis-Menten equation kinetics, as assessed through two computer-assisted procedures based on differential and integrated forms of this equation. Parameter values found were: Vm = 3.88-4.72 mg.ml-1.h-1 (43.6-52.9 mM.h-1), and Km = 0.97-1.13 mg.ml-1 (10.9-12.7 mM). Statistical analysis does not account for the existence of significant parallel passive diffusion pathways (less than 0.2 h-1).
Merino
M
M
Department of Pharmacology and Pharmaceutics, University of Valencia, Spain.
Polache
A
A
Peris-Ribera
J E
JE
Moreno-Dalmau
J
J
Plá-Delfina
J M
JM
D000409:Alanine / Q000378:metabolism*; D000818:Animals; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008433:Mathematics; D008962:Models, Theoretical; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D015091:beta-Alanine / Q000378:metabolism*
D015091:beta-Alanine; D000409:Alanine