TY - JOUR
T1 - Arginine synthesis does not occur during first-pass hepatic metabolism in the neonatal piglet
AU - Urschel, Kristine L.
AU - Shoveller, Anna K.
AU - Pencharz, Paul B.
AU - Ball, Ronald O.
PY - 2005/6
Y1 - 2005/6
N2 - We have shown that first-pass intestinal metabolism is necessary for ≃50% of whole body arginine synthesis from its major precursor proline in neonatal piglets. Furthermore, the intestine is not the site of increased arginine synthesis observed during dietary arginine deficiency. Primed constant intravenous (iv) and intraportal (ip) infusions of L-[U-14C]proline, and iv infusion of either L-[guanido-14C]arginine or L-[4,5- 3H]arginine were used to measure first-pass hepatic arginine synthesis in piglets enterally fed either deficient (0.20 g·kg -1·day-1) or generous (1.80 g·kg -1·day-1) quantities of arginine for 5 days. Conversion of arginine to other urea cycle intermediates and arginine recycling were also calculated for both dietary treatments. Arginine synthesis (g·kg-1·day-1) from proline was greater in piglets (P < 0.05) fed the deficient arginine diet in both the presence (generous: 0.07; deficient: 0.17; pooled SE = 0.01) and absence (generous: 0.06; deficient: 0.20; pooled SE = 0.01) of first-pass hepatic metabolism. There was no net arginine synthesis from proline during first-pass hepatic metabolism regardless of arginine intake. Arginine conversion to urea, citrulline, and ornithine was significantly greater (P < 0.05) in piglets fed the generous arginine diet. Calculated arginine fluxes were significantly lower (P = 0.01) for [4,5-3H]arginine than for [guanido-14C]arginine, and the discrepancy between the values was greater in piglets fed the deficient arginine diet (35% vs. 20%). Collectively, these findings show that first-pass hepatic metabolism is not a site of net arginine synthesis and that piglets conserve dietary arginine in times of deficiency by decreasing hydrolysis and increasing recycling.
AB - We have shown that first-pass intestinal metabolism is necessary for ≃50% of whole body arginine synthesis from its major precursor proline in neonatal piglets. Furthermore, the intestine is not the site of increased arginine synthesis observed during dietary arginine deficiency. Primed constant intravenous (iv) and intraportal (ip) infusions of L-[U-14C]proline, and iv infusion of either L-[guanido-14C]arginine or L-[4,5- 3H]arginine were used to measure first-pass hepatic arginine synthesis in piglets enterally fed either deficient (0.20 g·kg -1·day-1) or generous (1.80 g·kg -1·day-1) quantities of arginine for 5 days. Conversion of arginine to other urea cycle intermediates and arginine recycling were also calculated for both dietary treatments. Arginine synthesis (g·kg-1·day-1) from proline was greater in piglets (P < 0.05) fed the deficient arginine diet in both the presence (generous: 0.07; deficient: 0.17; pooled SE = 0.01) and absence (generous: 0.06; deficient: 0.20; pooled SE = 0.01) of first-pass hepatic metabolism. There was no net arginine synthesis from proline during first-pass hepatic metabolism regardless of arginine intake. Arginine conversion to urea, citrulline, and ornithine was significantly greater (P < 0.05) in piglets fed the generous arginine diet. Calculated arginine fluxes were significantly lower (P = 0.01) for [4,5-3H]arginine than for [guanido-14C]arginine, and the discrepancy between the values was greater in piglets fed the deficient arginine diet (35% vs. 20%). Collectively, these findings show that first-pass hepatic metabolism is not a site of net arginine synthesis and that piglets conserve dietary arginine in times of deficiency by decreasing hydrolysis and increasing recycling.
KW - Arginine biosynthesis
KW - First-pass metabolism
KW - Proline
UR - http://www.scopus.com/inward/record.url?scp=19444361964&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=19444361964&partnerID=8YFLogxK
U2 - 10.1152/ajpendo.00530.2004
DO - 10.1152/ajpendo.00530.2004
M3 - Article
C2 - 15657089
AN - SCOPUS:19444361964
SN - 0193-1849
VL - 288
SP - E1244-E1251
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 6 51-6
ER -