Uric Acid, Total Non-Protein Nitrogen and Urea Nitrogen in Blood
(The Figures represent Milligrams per 100 grams of Blood.)
| Uric acid. | Non-protein nitrogen. | Urea nitrogen. | |
|---|---|---|---|
| Human, group 1 | 0·8 | 36 | 19 |
| Human, group 2 | 1·5 | 34 | 18 |
| Human, group 3 | 2·8 | 36 | 19 |
| Human, with blood pressures of 160 | 2·9 | 50 | 33 |
| Human, with blood pressures of 200 | 1·2 | 50 | 22 |
| Human, with blood pressures of 220 | 2·7 | 40 | 19 |
| Human, with blood pressures of 260 | 3·9 | 52 | 20 |
| Human, alcoholic | 1·0 | 43 | 29 |
| Human, chronic gout | 3·9 | 25 | 13 |
| Human, chronic gout | 4·4 | 30 | 15 |
| Human, chronic gout | 5·2 | 20 | 13 |
| Human, lead poisoning | 4·7 | 50 | 31 |
| Human, lead poisoning | 4·8 | 52 | 32 |
| Human, leukæmia | 3·1 | 33 | 14 |
| Human, acute nephritis with arterio-sclerosis | 2·7 | 40 | 19 |
| Human, chronic nephritis with arterio-sclerosis | 2·5 | 38 | 19 |
Interesting and valuable as are the above findings, Folin and Denis are careful to point out that, even as regards the first three groups in the above table, “the figures can scarcely be said to represent the strictly normal variations, for no attempt was made to select physically normal persons.” The samples of blood were drawn from patients newly admitted to the Boston Psychopathic Hospital.
It may be noted that of all the mammals examined the blood of man contains by far the greatest amount of uric acid. Also that in humans the uric acid blood content varies in different persons, and, moreover, as Walker Hall points out, “the figures lend support to the view that there may be groups or families exhibiting similar features.” It will be seen, too, that the blood uric acid in gout and lead poisoning stands at a high level, though not so elevated as was formerly maintained. From the figures, too, it may be gleaned that apparently no relationship obtains between the amount of uric acid and that of the urea or total non-protein nitrogen in the blood.
At the same institution in Boston, Adler and Ragle conducted a similar series of investigations, though on a more extended scale. These observers, taking 156 unselected psychopathic patients, found that in 107 examples the uric acid content of the blood was from 1-2 mg., in thirty-eight more than 2 mg., and in eleven instances less than 1 mg. To sum up, the uric acid content varied from 0·7-4·5 mg. per 100 grams of blood, an average of 1·7 mg.
As before stated, it was until recently maintained that in the blood of normal individuals, on a purin-free diet, uric acid was undemonstrable. But McLester, utilising Folin’s method, found uric acid in the blood of fifteen healthy individuals, who had been on a purin-free diet for at least three days, and this in amounts ranging from 0·5-2·9 mg. per 100 grams of blood, an average of 1·4, as contrasted with 1·7, the average amount in Adler and Ragle’s series. Pratt, discussing these findings, considers that the fact that the average amounts approximate so nearly in the two series is worthy of emphasis. This especially as all McLester’s examples were young healthy adults on a purin-free diet, while the patients studied by Adler and Ragle were of all ages and on a mixed diet.[21]
Effect of Exogenous Purines
As we are aware, the amount of uric acid excreted in the urine increases markedly on a purin-rich diet. But recent researches appear to raise doubts as to whether the uric acid content of the blood rises correspondingly. Thus, according to Walker Hall, “a state of uricæmia is said to exist if the amount of uric acid in the blood exceeds 0·8 mg. per 100 c.c.” The figure he considers is probably too low for, after an average meat breakfast, the blood uric acid rises to 1 or 2 mg. per 100 c.c. in normal adults, or even higher after an excessive intake of purin-rich foods.
On the other hand, Denis, investigating the effect of ingested purin on the uric acid content of the blood, found that in normal individuals no increase in the circulating uric acid follows the intake; in other words, the kidney, in normal persons, is quite capable of excreting any excess of uric acid presented to it, thereby keeping the uric acid of the blood at the same level as obtains when only the endogenous moiety thereof has to be eliminated.