NITROGEN-BALANCE, PLASMA-FREE AMINO-ACID-CONCENTRATIONS AND URINARY OROTIC-ACID EXCRETION DURING LONG-TERM FASTING IN CATS

The purpose of this study was to ascertain the changes in nitrogen bal ance, plasma free amino acid concentrations, urinary erotic acid excre tion and body weight during long-term fasting in adult obese cats. Res ults from eight cats that fasted rather than eat an unpalatable diet a re reported. After 5 to 6 wk of weight loss, six of the eight cats dev eloped signs of hepatic lipidosis, and the livers of all cats were sev erely infiltrated with lipids. Cats lost (mean +/- SE) 33.2 +/- 1.4% o f their pre-fasting body weight. Mean nitrogen balance (+/-SE) was -54 7 +/- 54 mg.d(-1).kg-2/3 for the first week, and then the net nitrogen losses decreased to a plateau (-303 +/- 52 mg.d(-1).kg-2/3) after 4 w k. Easting was associated with a decrease in plasma concentration of e ssential amino acids. When plasma amino acid concentrations were consi dered individually, concentrations of alanine, methionine, taurine, ci trulline, arginine and tryptophan decreased the most (greater than or equal to 50%), whereas concentrations of glutamine, glutamate and orni thine significantly increased. Orotic acid was not detected in the uri ne during the fast. After 1 wk of fasting, obese cats had reduced nitr ogen excretion, but not to the same extent as has been shown in obese humans or obese rats. It is suggested that the availability of several amino acids may become limiting for liver protein synthesis during fa sting and that these deficiencies may contribute to the development of hepatic lipidosis. Orotic acid was not linked to hepatic lipidosis ca used by fasting in cats.