Absorption kinetics of β-alanine as model compound in rat small intestine

• Published in: Biochimica et biophysica acta Vol. 986; no. 1; pp. 1 - 7
• Main Authors: MERINO, M, POLACHE, A, PERIS-RIBERA, J. E, MORENO-DALMAU, J, PLA-DELFINA, J. M
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 17.11.1989; North-Holland
• Subjects: Alanine - metabolism; Animals; beta-Alanine - metabolism; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Intestinal Absorption; Intestine, Small - metabolism; Intestine. Mesentery; Kinetics; Male; Mathematics; Models, Theoretical; Perfusion; Rats; Rats, Inbred Strains; Vertebrates: digestive system; Alanine; Statistical analysis; Rat; Rodentia; Small intestine; Vertebrata; Mammalia; Absorption; Antispasmodic agent; Michaelis constant; Perfusion; Aminoacid; Kinetics; Kinetic parameter; Computer aided analysis
• ISSN: 0006-3002; 1878-2434
• DOI: 10.1016/0005-2736(89)90264-2

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).