Urea utilization by rabbits fed a low-protein ration

¹ Laboratories of Physiology and Pharmacology, Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Utilization of urea by adult rabbits fed straw, carrots, and sucrose was investigated. 1) In a 24-hr period following intravenous injection of 290 mg urea-N/kg body wt., part of the exogenous urea was excreted in urine and part was stored in body fluids; the remainder could not be accounted for and was presumed utilized in amino acid synthesis. An average of 212 ± 54 (sd) mg urea-N were utilized in eight such experiments (control urea-N excretion was 151 mg/day). Urea given per os over several days was also utilized. 2) When drinking water was removed, utilization of urea given per os, as reflected in nitrogen balance, increased; or, if no urea was given, nitrogen excretion decreased. 3) Antibacterial agents per os reduced exogenous urea utilization; or, if no urea was given, urea excretion increased, representing endogenous urea normally utilized (up to 40% of that formed in the body). 4) In acute experiments, blood urea moved into the saline-filled cecum at rates commensurate with the rates of utilization found in the other experiments. It was concluded that adult rabbits under these conditions can utilize urea at rates significant in nitrogen metabolism.

Key Words: cecal function • antibacterial agents • water deprivation and urea excretion • alimentary microorganisms • endogenous urea • amino acid synthesis

Submitted on April 1, 1963