[Passage of endogenous urea into a jejunum of sheep]

The quantitative passage of urea-N and ammonia N into an isolated jejunum of the merino sheep was studied within one hour before, and 1, 2, 3, 4 and 5 hours after feeding. The total amount of ammonia-N that passes to the isolated jejunum [to both proximal and distal part] within an hour is small [0.28-0.35 mg h-1], without any significant differences in passage prior to and after feeding. However, urea-N secretion is high, especially secretion to the fore part of the jejunum [ 3.35-3.62 mg h-1]. The passage of urea-N to the rear part of the jejunum is about 1/3 lower than passage to the fore part. Urea solution of higher concentration than in peripheral blood was incubated in the isolated jejunum to study an adverse phenomenon: absorption of urea from intestinal lumen to the blood. The levels of urea in peripheralblood and in incubate reached a balance state within one hour after administration. The data obtained testify to the permeability of the wall of the gut for urea in both directions.