Urea synthesis in moderate experimental uremia.
Urea synthesis rates (USR) were examined in relation to individual variations in energy and nitrogen intakes. Rats made uremic by 7/8 nephrectomy (N = 12) were pairfed with sham-operated controls (N = 11) and divided into two diet groups: diet 1 (4 kcal/g, 18% protein) and diet 2 (4 kcal/g, 42% protein). Nitrogen intake (NI) and energy intake (EI) were varied according to the quantity of feed given and the addition of a nonprotein gavage supplement. The USR was determined by 14C-urea excretion during four periods when EI ranged from 20 to 50 kcal/day and NI ranged from 150 to 675 mg/day. Although USR did not correlate directly with either dietary protein or energy, the percent of protein-derived calories allowed the prediction of USR from NI. Fractional urea synthesis was not related to NI but rather to total EI. The nonlinear regression described a critical EI of 30 kcal/day below which USR increased to 75% of the NI. USR was not different between control and uremic animals. These data suggest an advantage in maintaining an appropriate protein: energy ratio (2.5 g per 100 kcal) to minimize the fractional urea synthesis. The utilization of nitrogen at different levels of protein and energy intake was not altered by the state of experimental uremia.
D000818:Animals; D004044:Dietary Proteins; D002149:Energy Intake; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D051381:Rats; D014508:Urea / Q000096:biosynthesis*; D014511:Uremia / Q000378:metabolism*
D004044:Dietary Proteins; D014508:Urea; D009584:Nitrogen