Sodium-dependent alanine transport in brush border membrane vesicles from ventral colon of the horse [microform]
- Bib ID:
- 3283082
- Format:
- Book and Microform
- Author:
- Lew, John P
- Description:
- 114 p.
- Summary:
-
Na$\sp+$-dependent uptake of L-alanine against a concentration gradient was demonstrated in isolated brush border membrane vesicles from the equine ventral colon. The vesicles were prepared by selective membrane treatment with CaCl$\sb2$ and differential centrifugation. Uptake studies were determined by a conventional rapid filtration technique. In the presence of an initial NaCl gradient (100 mM outside the vesicles to 0 mM inside), L-alanine uptake displayed the typical "overshoot" curve reflecting the secondary active transport of the amino acid against its concentration gradient. The overshoot peak (maximum accumulation) of greater than twice the equilibrium value was reached after 12 min. Equilibrium was attained after 4 hr. Under the same conditions, D-alanine uptake never exceeded the equilibrium value. When KCl replaced NaCl, both isomers followed the uptake curve displayed by D-alanine in the presence of a NaCl gradient.
LiCl partially substituted for NaCl in L-alanine uptake while a D-mannitol gradient had the same effect as that of KCl. Equilibrium uptake values of both isomers under initial NaCl gradient were found to be inversely proportional to the extravesicular medium osmolarity, thus demonstrating uptake into an osmotically active intravesicular space. L-methionine, L-threonine and L-leucine strongly inhibited Na$\sp+$-dependent L-alanine uptake whereas glycine and L-proline inhibited to a lesser degree. L-phenylalanine and L-aspartic acid were weaker inhibitors and L-lysine was inactive. Na$\sp+$-dependent L-alanine uptake was determined to be mediated by at least 2 carrier systems having the following kinetic parameters (values from 2 horses): (1) a K$\sb{\rm t}$ of 0.102 or 0.185 mM and a V$\sb{\rm max}$ of 25.3 or 45.7 pmol.mg$\sp{-1}$ protein.s$\sp{-1}$; (2) a K$\sb{\rm t}$ of 1.25 or 1.57 mM and V$\sb{\rm max}$ of 113 or 114 pmol.mg$\sp{-1}$ protein.s$\sp{-1}$.
Inhibition by L-methionine was competitive with K$\sb{\rm i}$'s for the 2 systems of 0.32 $\pm$ 0.15 and 3.71 $\pm$ 1.20 mM respectively. No Na$\sp+$-dependent D-glucose uptake could be shown in these vesicles. The data strongly support the contention that the equine large intestine can absorb amino acids against a concentration gradient.
- Notes:
-
- (UnM)AAI9007428
- Source: Dissertation Abstracts International, Volume: 50-10, Section: B, page: 4292.
- Co-Directors: John P. Baker; Donald F. Diedrich.
- Thesis (Ph.D.)--University of Kentucky, 1989.
- Reproduction:
- Microfiche. Ann Arbor, Mich.: University Microfilms International.
- Subject:
- Agriculture, Animal Culture and Nutrition
- Other authors/contributors:
- University of Kentucky
- Copyright:
-
In Copyright
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Copyright status was determined using the following information:
- Material type:
- Literary Dramatic Musical
- Published status:
- Unpublished
- Creation date:
- 1989
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