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 variati ons in dietary protein intake, on splanchnic amino acid balances. Two serie s of 30-day-old male lean (Fa/?) Zucker rats were fed ad libitum for 30 day s 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 After 30 days of dietary treatment , blood was withdrawn from hepatic vein, portal vein and arterial aorta in one set of rats.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 de termined using fluorescent microspheres, From the individual amino acid con centration 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 Gin and Cit and a net r elease of Pro, Ala and Gly. The LP group showed the same pattern, with incr eased release of Ala and Gly. In contrast to this limited amino acid releas e, the HP group showed a generalized net release of amino acids from the in testine. The RD group only show a net Gin release from the liver. Conversel y, the HP group showed net uptake of Gin, Pro, Ala, Tyr and Lys, and the LP group took up Gly and Ala and released Asn, Gin and Cit. Our results indic ate that growing Zucker rats respond to long-term moderate changes in the p rotein 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 f ollowed a similar pattern of intestinal balance for Ala, Gin, 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 Gin by intest ine probably due to an increased release of Ala instead of Gin from periphe ral tissues.