Uric acid and urea in relation to protein catabolism in long-term fasting geese

Abstract

Five ganders were subjected to an experimental fast comparable to that which spontaneously occurs during breeding in domestic geese, and during migration and breeding in various wild birds. Plasma uric acid and urea concentrations, and their excretion as a proportion of total nitrogen excretion, were studied in relation to daily change in body mass per unit body mass, mg/mdt. This variable has previously been found to reflect changes in protein catabolism over the three phases of fast: I, dm/mdt and protein utilization both decrease; II, they are maintained at a low value; and III, they increase. In the fed state, daily total nitrogen excretion was 5 gN X 24 h-1; uric acid, ammonia and urea accounted for 51, 15 and 5% respectively. The high remaining proportion of excreted nitrogen (29%), after subtraction of uric acid-N, ammonia-N and urea-N to total nitrogen, accords with the literature. During fasting, the changes in daily excretion of uric acid, urea, ammonia and total nitrogen followed a pattern essentially similar to that for dm/mdt. Uric acid accounted for a progressively increasing fraction of total nitrogen, up to 76% at the end of phase III, while urea remained at a constant 5%. Plasma concentrations of both uric acid and urea followed similar trends during the fast, in particular both increasing during phase III, i.e. when there was a rise in nitrogen excretion. This suggests they could be used as an index in field investigations, to determine whether birds which naturally fast in connection with specific activities have entered into the situation where proteins are no longer spared.

Effects of food limitation on the intensity of blue‐green and brown eggshell coloration: an experimental study with the canary

“…For example, uric acid is the result of protein and purine catabolism (Robin et al 1987, Wright 1995, and it is also known to have antioxidant properties (Machín et al 2004, Stinefelt 2005, Cohen et al 2007, Alan and McWilliams 2013. It is possible that due to the lower protein intake, there was a decline in levels of uric acid (Cohen et al 2009, Alan andMcWilliams 2013) and methionine, which can be converted to cysteine and then to glutathione (Li et al 2002, Métayer et al 2008, Swennen et al 2011, and in the synthesis and activity of some antioxidant enzymes (Feoli et al 2006), and thus females experienced a lower total antioxidant capacity.…”

The low-affinity glucocorticoid receptor regulates feeding and lipid breakdown in the migratory Gambel's white-crowned sparrowZonotrichia leucophrys gambelii

“…Free fatty acids and glycerol are released when triglycerides are hydrolyzed and indicate lipid mobilization from adipose tissue (Elia et al, 1987;Scow and Chernick, 1970). Uric acid results from the breakdown of protein, which can originate from either the muscle or the diet (Lindgård et al, 1992;Robin et al, 1987). β-hydroxybutyrate is synthesized predominantly during fasting to replace part of the glucose supply and suggests lipid catabolism and glucose shortage (Robinson and Williamson, 1980).…”

Role of the Low‐Affinity Glucocorticoid Receptor in the Regulation of Behavior and Energy Metabolism in the Migratory Red KnotCalidris canutus islandica

“…Free fatty acids and glycerol are released when triglycerides are hydrolyzed and indicate lipid mobilization from adipose tissue (Scow and Chernick 1970;Hurley et al 1986;Elia et al 1987). Uric acid results from the breakdown of protein that originates from bodily tissue or the diet (Mori and George 1978;Robin et al 1987;Lindgård et al 1992). Concentrations of each of the five plasma metabolites were compared among the three treatment groups with a one-way ANOVA.…”