Urea production is increased in neonatal piglets infused with alanine at 25, 50, and 75% of resting energy needs .

To study the ability of neonatal piglets to metabolize a nitrogen load and excrete it as urea, 12 newborn piglets, 6 small (0.99 +/- 0. 16 kg; expt. 1) and 6 large (1.86 +/- 0.16 kg; expt. 2), were infused intravenously with alanine (n = 8; 4 large, 4 small; treatment) or glucose (n = 4; 2 large, 2 small; control) at equal ATP equivalents, supplying 25-75% of the resting energy requirements of the piglet over 18 h. To adjust for differences in the baseline urinary urea nitrogen excretion, blood urea nitrogen (BUN) and estimated urea production between groups, the absolute changes from baseline to maximum value for piglets infused with alanine, and from baseline to the 24-h value for piglets infused with glucose were evaluated statistically. There were no differences (0.1 < P < 0.3) in the absolute changes from baseline to maximum values of urinary urea nitrogen, BUN or estimated urea production between small [18.6 +/- 3.8 mg N/(h. kg(0.75)); 19.1 +/- 2.2 mmol N/L; 2.7 +/- 1.2 mmol N/(h. kg(0.75)), respectively] and large [23.6 +/- 7.6 mg N/(h. kg(0. 75)); 21.6 +/- 3.3 mmol N/L; 3.7 +/- 1.5 mmol N/(h. kg(0.75)), respectively] piglets infused with alanine. Differences in the changes from baseline were detected between alanine and glucose (P = 0.001) infusions. Small piglets required more time (P < 0.005) for BUN to maximize after initiation of the alanine infusion, suggesting that small piglets require more time to process a nitrogen load. Infusion of alanine resulted in at least a threefold increase from baseline in the rate of calculated urea production, suggesting that neonatal piglets, small or large, have reserve capacity to metabolize nitrogen and excrete it as urea.