Determination of creatinine in urine by separation on DEAE-Sephadex and ultraviolet spectrophotometry

The origin of urinary aromatic compounds excreted by ruminants. 1. The metabolism of quinic, cyclohexanecarboxylic and non-phenolic aromatic acids to benzoic acid

1. The contribution of dietary constituents to the large urinary output of benzoic acid characteristic of ruminants and some herbivores is not well understood. 2. Methods for the analysis of quinic, cyclohexanecarboxylic, benzoic, phenylacetic, 3-phenylpropionic and cinnamic acids in urine and in rumen fluids were developed. 3. The urinary output of aromatic acids by sheep given seven-rations was determined: benzoic acid output varied between 2.8 and 7.8 g/d; phenylacetic acid output between 0.16 and 1.3 g/d; cinnamic acid between 0.08 and 0.25 g/d and small amounts of 3-phenylpropionic acid were found in some samples. 4. Increments in urinary aromatic acid excretion were determined when the acids listed in paragraph 2 were infused via rumen or abomasal cannulas. 5. When cyclohexanecarboxylic acid was infused 40% of the dose was excreted as urinary benzoic acid after either route of infusion. Quinic acid was completely metabolized in the rumen; following rumen infusion between 16 and 53% of the infused acid was recovered as urinary benzoic acid; none was so recovered after abomasal infusion. 6. Urinary recoveries of rumen- and abomasally-infused aromatic acids were: benzoic acid 90 and 88% respectively as benzoic acid, phenylacetic acid 78 and 83% respectively as phenylacetic acid, 3-phenylpropionic acid 96 and 105% respectively as benzoic acid and cinnamic acid, 70 and 70% respectively as benzoic acid. 7. The concentration of aromatic acids in rumen fluid varied with time after feeding: cyclohexanecarboxylic acid was maximal (7 mg/l) 1 h after feeding, benzoic acid was always a minor component (0.5 +/- 0.5 mg/l), phenylacetic acid varied between 0 and 35 mg/l and 3-phenylpropionic acid between 25 and 47 mg/l. Cinnamic acid was not found in rumen fluid but on rumen infusion of this acid the concentration of 3-phenylpropionic acid in rumen fluid increased by 10 mg/l rumen fluid per g infused per d. 8. The incomplete metabolism of quinic and cyclohexanecarboxylic acids to urinary benzoic acid is discussed. It is concluded that the principal dietary precursors of urinary benzoic acid in ruminants are compounds yielding 3-phenylpropionic acid on microbial fermentation in the rumen. The small amount of cinnamic acid characteristic of ruminant urine arises as an intermediate in the beta-oxidation of 3-phenylpropionic acid in the body tissues.

Towards a definitive assay of creatinine in serum and in urine: separation by high-performance liquid chromatography

A fast and sensitive method for the separation of serum and urinary creatinine is described. For the preliminary purification of serum and urine, a cation-exchange column is used to remove protein, anions and neutral compounds prior to isolation of creatinine by high-performance liquid chromatography. A reversed-phase system with 0.01 M ammonium acetate solution as the mobile phase can separate creatinine in 7.5 min at a flow-rate of 1 ml/min. The purity of the separated creatinine is proved by derivatization using trifluoracetic anhydride, followed by gas chromatography and mass spectrometry. Although this method of purification was designed for incorporation into a definitive assay, the ease and speed of analysis makes is very attractive for routine clinical use.

The urinary aromatic acids excreted by sheep given S24 perennial ryegrass cut at six stages of maturity

1. S 24 perennial ryegrass was harvested at six stages of its growth from young leafy herbage to mature grass in which the seed had shed.

2. Two sheep were offered 1kg/d of each cut and two other sheep were offered 750 g/d of each cut of grass.

3. The contents of some possible precursors of the urinary aromatic acids excreted by sheep, namely, shikimic acid, quinic acid, chlorogenic acid, total o-dihydroxyphenolic compounds, lignin and crude protein were determined in each cut of grass.

4. A gas-liquid chromatographic method for the determination of the aromatic acids present in light petroleum extracts of urine was developed.

5. The urinary excretion of creatinine, diethyl ether-soluble acids, hippuric acid, total benzoic, phenylacetic and phenylpropionic acids, and the apparent digestibilities of nitrogen, lignin and dry matter were determined with each sheep offered each cut of grass.

6. The quantity of the various aromatic acid fractions excreted by sheep decreased as the maturity of the herbage increased and was directly proportional to the amount of food consumed.

7. No relationship was found between the intake of possible benzoic acid precursors and the urinary excretion of benzoic acid. With diets of young herbage, smaller amounts of benzoic acid were excreted in the urine than would be predicted from the intakes of the precursors studied, and with mature herbage greater amounts were excreted than would be predicted.

8. Possible reasons for these results are discussed, and the nature of additional precursors of urinary aromatic acids excreted by sheep given mature herbages are considered.

9. Urinary excretion of phenylacetic acid varied with diet in a manner which closely followed the intake of apparently digestible nitrogen. A highly significant (P < 0.001) exponential relationship was found between these two variables; it was log10E = 0.05 N –0.63, where E is the urinary phenylacetic acid output (g/kg food) and N the intake of apparently digestible nitrogen (g/kg food).

The urinary excretion of aromatic acids by starved sheep

1. Four wether sheep were maintained on a diet of hay for 2 weeks and then starved for a period of 4 days.

2. Immediately before and during starvation the urinary excretion in the following fractions was determined: hippuric acid, creatinine, total diethyl ether-soluble acids of hydrolysed and unhydrolysed urine, total aromatic acids in hydrolysed and unhydrolysed urine and the proportion of the former present as benzoic and phenylacetic acids.

3. A method for determining the benzoic acid content of light petroleum extracts of urine has been developed and is described.

4. Starvation had little effect on the urinary excretion of phenylacetic acid or creatinine, but during the first 2 days of starvation there were large decreases in the excretion of all the other urinary fractions studied.

5. Of the fractions examined, 43% of the diethyl ether-soluble acids of hydrolysed urine and 42% of those of unhydrolysed urine were of exogenous origin; 76% of the total urinary aromatic acids were of exogenous origin. Partition of the aromatic acids in the urine of two of the four sheep indicated that the reduction in aromatic acid excretion on starvation was completely accounted for by the decline in benzoic acid output. Almost all the hippuric acid (97%) was of exogenous origin.

6. These results have been compared with the urinary output of aromatic acids by nonruminants when fasted, and possible reasons for the relatively large amounts of phenylacetic acid found in the urine of starved sheep have been discussed.