Gluconeogenesis and ureagenesis might be integrated and energy expensive processes and, thus, a trial was conducted to measure the impact of the mesenteric infusion of different N compounds on oxygen uptake by splanchnic tissues of wethers. The trial was conducted with 4 multicatheterized wethers as a 4 × 4 Latin square with 210-min daily periods. The blood flow through portal-drained viscera (PDV) and liver was determined by downstream dilution of 15 g/L p-aminohippurate (PAH) infused continuously (1.5 mL/min) into the mesenteric vein. In parallel, wethers were continually infused into the mesenteric vein with a saline (0.15 M NaCl) solution during 90 min followed by the infusion, during more 120 min, of either: saline (control), 0.25 M NH₄HCO₃, 0.25 M L-alanine or 0.125 Ml-arginine, all of them infused at a rate of 1.5 mL/min to provide 375 µmol N/min. Throughout infusion periods simultaneous arterial, portal and hepatic blood samples were taken at 30 min interval and analyzed for PAH and oxygen concentration. The PROC MIXED of SAS was used for variance analysis, which generated a residual error. The oxygen uptake during treatment infusion (i.e., 90 to 210 min) was compared with that of control period (i.e., first 90 min) within each treatment by F test. Oxygen uptake by PDV during treatment infusion was not different from that observed during saline infusion for any treatment, whereas only NH₄HCO₃ infusion increased oxygen uptake by liver (Table 1). In conclusion, increased ammonia load increased energy expenditure by liver of wethers. Table 1. Oxygen uptake (mL/h) by portal-drained viscera (PDV) and liver of wethers infused with saline (NaCl) or with 375 µmol N/min of different N compounds into the mesenteric vein

Item	Time (min)1	Infusion treatments				SEM
NaCl	Ammonia	Alanine	Arginine
PDV	0-90	2871	2692	3210	3532	580.2
	90-210	2857	2579	3115	3583	280.5
P*		0.981	0.822	0.880	0.948
Liver	0-90	1600	1617	2164	3154	316.6
	90-210	1917	2583	2460	2548	246.5
P*		0.453	0.045	0.385	0.157

¹Saline solution was used through the first 90 minutes in all treatments. *Probability of the difference between 90-210 vs. 0-90 min means.