Intestinal arginine metabolism during development. Evidence for de novo synthesis of L-arginine in newborn pig enterocytes.
The capacity for L-arginine metabolism was studied in villus enterocytes isolated from pigs at birth, after 2-8 days suckling and after weaning. Immediately after birth, enterocytes were able to convert 1 mM L-citrulline, 2 mM L-glutamine or 1 mM L-ornithine to L-arginine. In 2-8-day-old animals, the net production of L-arginine from L-citrulline (2.00 +/- 0.45 nmol x 10(6) cells-1 x 30 min-1), or from L-ornithine (0.29 +/- 0.06 nmol x 10(6) cells-1 x 30 min-1) was similar to the values obtained at birth. Furthermore, 40% of L-arginine synthetized de novo from L-citrulline were released into the incubation medium. In 2-8-day-old animals, the production of L-arginine from L-glutamine represented only 5% of the production at birth (the latter being 0.73 +/- 0.15 nmol x 10(6) cells-1 x 30 min-1). In enterocytes isolated from post-weaned pigs, no significant production of L-arginine from either L-glutamine or L-ornithine was detected. In contrast, although the L-arginine production from L-citrulline was very low in post-weaned animals, it was significantly enhanced in the presence of L-glutamine, representing 23% of the production measured in suckling animals. The capacity of enterocytes to cleave L-arginine to L-ornithine and urea was very limited at birth, but was increased more than threefold in 2-day-old animals. This was concomitant with a marked increase in arginase activity. In post-weaned animals, the flux through arginase in intact enterocytes, and the arginase activity were both threefold higher than in 2-8-day-old animals. It is concluded that enterocytes isolated from neonatal pigs exhibit the capacity for a net production of L-arginine since the metabolism of this amino acid is oriented to anabolism rather than catabolism. The results are discussed in relation to L-arginine metabolism in the neonatal liver.
Blachier
F
F
Unité d'Ecologie et de Physiologie du Système Digestif, Institut National de la Recherche Agronomique, Jouy-en-Josas, France.
M'Rabet-Touil
H
H
Posho
L
L
Darcy-Vrillon
B
B
Duée
P H
PH
D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D001120:Arginine / Q000096:biosynthesis* / Q000378:metabolism; D002221:Carbamyl Phosphate / Q000032:analysis; D002469:Cell Separation; D002851:Chromatography, High Pressure Liquid; D002956:Citrulline / Q000378:metabolism; D005260:Female; D005973:Glutamine / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D009952:Ornithine / Q000378:metabolism; D009954:Ornithine Carbamoyltransferase / Q000378:metabolism; D011247:Pregnancy; D013552:Swine
D005973:Glutamine; D002956:Citrulline; D002221:Carbamyl Phosphate; D001120:Arginine; D009952:Ornithine; D009954:Ornithine Carbamoyltransferase