Proline ameliorates arginine deficiency during enteral but not parenteral feeding in neonatal piglets

The indispensability of arginine has not been conclusively established in n ewborns. Because parenteral feeding bypasses the gut (where de novo synthes is of arginine occurs from proline), a dietary supply of arginine that is s ufficient to maintain urea cycle function may be of greater importance duri ng intravenous compared with enteral feeding. Two-day-old piglets (n = 12) were fed nutritionally complete diets for 5 days via either a central vein catheter (TV pigs, n = 6) or a gastric catheter (IG pigs, n = 6). Subsequen tly, each piglet received three incomplete test diets [arginine free (-ARG/ +PRO), proline free (-PRO/+ARG), or arginine and proline free (-ARG/-PRO)] in a randomized crossover design. Plasma ammonia was assayed every 30 min f or 8 h or until hyperammonemia was observed. Ammonia increased rapidly in T V pigs receiving -ARG/+PRO and -ARG/-PRO (84 +/- 36 and 74 +/- 37 mu mol.l( -1).h(-1), respectively), requiring early diet cessation. A rapid increase was also exhibited by IG pigs receiving the -ARG/-PRO, but not the -ARG/+PR O diet (31 +/- 15 vs. 11 +/- 7 mu mol.l(-1).h(-1), respectively, P < 0.05). Plasma arginine and proline were indicative of deficiency (IG and TV group s) when deplete diets were infused. Arginine is indispensable in parenteral and enteral nutrition, independent of dietary proline.