Source of Endogenous Purins
Is the nuclear destruction of localised or generalised distribution?
Mares (and subsequently many other observers), having noted that, following the ingestion of purin-free protein food, a marked increase in endogenous uric acid excretion ensued, suggested that the said augmentation was the outcome of the “wear and tear” entailed upon the nuclear material of the secretory glands of the gastro-intestinal tract, following such intake.
The effects yielded on uric acid excretion by those antithetic drugs, atropine and pilocarpine, certainly seem to lend colour to Mares’ hypothesis.
Following the injection of atropine, the rise in uric acid output, that normally follows the ingestion of protein, was inhibited. But in sequence to pilocarpine, an excitant and not like atropine, a depressor of secretory activity, a marked increase in uric acid excretion followed. The contrast in response was naturally translated as striking evidence of the important rôle played by the digestive glands on uric acid excretion; in other words, it was held that the major portion of the endogenous uric acid was the reflex of such intensified glandular action.
In opposition, however, Burian, as the outcome of his experimental studies, maintained that a fractional portion only of the endogenous uric acid could be derived from the nucleo-protein of the body cells. This, inasmuch as it would entail a far too extensive katabolism of nuclear substance. Accordingly he propounded the view that the endogenous uric acid in the main was derived from the hypoxanthine of the inosinic acid present in muscular tissue. In this connection it may be noted that, on a diet approximating to Voit’s standard, 0·5 gram of purin is excreted daily. This, it is calculated, is equivalent to nearly 100 grams of thymus or allied tissue, which probably far exceeds the amount that could be gleaned from cellular katabolism.