Phenylalanine transport in rabbit small intestine.
1. The proposal that rabbit small intestine possesses a separate, sodium-dependent carrier of phenylalanine has been examined by measurements of the unidirectional influx of amino acids across the brush-border membrane of the intact epithelium of the rabbit small intestine. 2. We demonstrate that, like alanine, glycine and leucine, phenylalanine shares sodium-dependent as well as sodium-independent transport with lysine. 3. Using the distal ileum we applied the A (phenylalanine)-B (leucine)-C (alanine) test on the sodium-dependent, lysine-resistant transport of phenylalanine. For phenylalanine, K1/2 (concentration required for half-maximal transport) was 3.1 +/- 0.2 mM (n = 7) and Ki (inhibitor constant) against leucine transport was 3.1 +/- 0.2 mM (n = 4). For leucine, K1/2 was 1.1 +/- 0.1 mM (n = 4) and Ki against transport of phenylalanine was 1.1 +/- 0.1 mM (n = 4). For alanine, K1/2 was 12.6 +/- 1.1 mM (n = 3), Ki against phenylalanine was 13.1 +/- 1.8 mM (n = 4) and Ki against leucine was 11.0 +/- 0.4 mM (n = 4). 4. Using the jejunum we applied the A (phenylalanine)-B (alanine)-C (methionine) test on the lysine-resistant, sodium-dependent transport of phenylalanine. For phenylalanine, K1/2 was 4.7 +/- 0.2 mM (n = 7) and Ki against alanine was 4.8 +/- 0.2 mM (n = 4). For alanine, K1/2 was 15.6 +/- 0.8 mM (n = 7) and Ki against phenylalanine was 18.1 +/- 0.9 mM (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
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D000409:Alanine / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D005260:Female; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008715:Methionine / Q000494:pharmacology; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism* / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000502:physiology
D010649:Phenylalanine; D012964:Sodium; D008715:Methionine; D007930:Leucine; D008239:Lysine; D000409:Alanine