Splanchnic amino acid balance is affected by moderate variations of dietary protein in the developing Zucker rat.
This study attempted to determine the influence of moderate chronic variations in dietary protein intake, on splanchnic amino acid balances. Two series of 30-day-old male lean (Fa/?) Zucker rats were fed ad libitum for 30 days with either a standard diet (reference diet: RD), a high-protein diet (HP) (35%) or a low-protein diet (LP) (9%). After 30 days of dietary treatment, blood was withdrawn from hepatic vein, portal vein and arterial aorta in one set of rats. In another series the splanchnic organ blood flows were determined using fluorescent microspheres. From the individual amino acid concentration in each sample and the blood flows, we calculated the intestinal and hepatic balances. There were no significant differences in the hepatic arterial, portal or supra-hepatic flows induced by dietary protein content. The RD group showed a marked intestinal uptake of Gln and Cit and a net release of Pro, Ala and Gly. The LP group showed the same pattern, with increased release of Ala and Gly. In contrast to this limited amino acid release, the HP group showed a generalized net release of amino acids from the intestine. The RD group only show a net Gln release from the liver. Conversely, the HP group showed net uptake of Gln, Pro, Ala, Tyr and Lys, and the LP group took up Gly and Ala and released Asn, Gln and Cit. Our results indicate that growing Zucker rats respond to long-term moderate changes in the protein intake, diminishing the growth pattern only in the LP group, but not in the HP group. In spite of the limited amino acid supply, the LP group followed a similar pattern of intestinal balance for Ala, Gln, Pro, Gly and Cit, as showed by the RD group. On the other hand, excess of dietary amino acids in the HP group seems to promote a lower utilization of Gln by intestine probably due to an increased release of Ala instead of Gln from peripheral tissues.
Masanés
R M
RM
Group Nitrogen-Obesitat, Department de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain.
Rafecas
I
I
Remesar
X
X
D000596:Amino Acids / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D001012:Aorta, Abdominal; D002851:Chromatography, High Pressure Liquid; D004044:Dietary Proteins / Q000008:administration & dosage*; D006503:Hepatic Veins; D008297:Male; D008863:Microspheres; D011169:Portal Vein; D051381:Rats; D011924:Rats, Zucker; D013152:Splanchnic Circulation / Q000502:physiology*
D000596:Amino Acids; D004044:Dietary Proteins