Changes in urea nitrogen and creatinine concentrations in the vitreous humor of cattle after death.

The mean urea nitrogen concentration in vitreous humor (VUN) in 97 healthy steers after death was 15.7 mg/dl. The mean serum urea nitrogen concentration in the same cattle was 20.0 mg/dl. The mean vitreous creatinine (VC) concentration was 0.7 mg/dl, and the serum creatinine value was 1.5 mg/dl. The VUN and VC were both significantly lower than serum urea nitrogen and serum creatinine, respectively, but varied in a consistent, predictable manner. In tests with 10 cows, postmortem intervals as long as 36 hours and ambient temperatures up to 30 C had no significant effects on VUN and VC. Evaluation of 8 animals with uremia confirmed that the vitreous humor is a stable fluid compartment after death, usable as an indicator of serum urea nitrogen and creatinine.