The effect of changes in the intestinal flow of nucleic acids on allantoin excretion in the urine of Sheep

Abstract

SUMMARYThree ewes were intraduodenally infused with yeast RNA (15, 20 and 30 g/day) or control solutions for 3 days and the net changes in urinary allantoin excretion determined. Four mature wethers fitted with a re-entrant cannula in the proximal duodenum were fed two levels (0·66 and 1 × maintenance) of pelleted lucerne hay. Allantoin excretion was compared with total nucleic acid (NA) flow in the small intestine.The average proportion of the recovery of the infused RNA-N dose as urinary allantoin–N amounted to 0·119 ± 0·0046. The values of the net increase of allantoin-N (Y, g/day) above control levels were highly significantly correlated (n = 12, r = 0·98) with amounts of RNA-N infused (X, g/day): y = 0·1185 (± 0·0086) X–0·004 (P < 0·001). The average ratio of urinary allantoin-N to NA-N passing the duodenum during 24 h was 0·173. A difference between the two conversion factors is discussed in relation to endogenous allantoin excretion and purine base composition of yeast and bacterial RNA.

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

“…Since exogenous purines can enter salvage pathways and used as substrates for tissue NA synthesis in ovine species (Ellis and Bleichner, 1969b;Smith etal., 1974;Razzaque etal., 1981;Kahn, 1991, cited by Kahn andNolan, 1993), urinary recoveries of infused purines reported in sheep have been subject to considerable variation (Table 3). Data from early experiments (Antoniewicz et al, 1980;Giesecke et al, 1984;Fujihara et al, 1987) was interpreted assuming a linear relationship between exogenous purine supply and urinary PD excretion, with the implication that PD excretion derived from endogenous sources remains constant across a range of exogenous purine loads. More recent observations have lead to the suggestion that this relationship is curvi-linear (Chen et al, 1990a(Chen et al, , 1997Balcells et al, 1991;Puchala and Kulasek, 1992;), due to the contribution of de novo purine synthesis at low exogenous purine loads necessary to compensate for limited amounts of absorbed exogenous purines entering salvage pathways, constituting a net endogenous purine loss.…”

Microbial protein production determined by urinary allantoin and renal urea sparing in normal and low protein fed Corriedale sheep

“…The nucleic acids synthesized by rumen microorganisms are enzymatically degraded to purine and pyrimidine bases which are absorbed; their final products are excreted in the urine with allantoin being in the greatest proportion [10]. Several authors have revealed a close relationship between microbial nucleic acids reaching the small intestine and the urinary excretion of purine derivatives, specially allantoin [1,18].…”

Reassessing the manipulation of protein synthesis by rumen microbes

“…Furthermore, the mechanisms involved in microbial attachment vary with species (Roger, 1990) (Antoniewicz et al, 1980;Giesecke et al, 1984). However, intermediate metabolites (hypoxanthine, xanthine and uric acid), which may be excreted in large and variable amounts, should be enzymatically converted into allantoin before the determination (Fujihara etal, 1987;Chen et al, 1993;Resines et al, 1993) or be separately quantified (Balcells et al, 1991(Balcells et al, , 1993.…”