Urinary Hyaluronidase

GINETZINSKY recently described a relationship between urinary hyaluronidase and urine concentration 1 . He found that urinary hyaluronidase assayed by his method was high at low urine volumes, virtually disappearing during water diuresis; but it remained high during an osmotic diuresis. From these results he inferred that antidiuretic hormone might act by stimulating the production of hyaluronidase within the nephron; this would facilitate water re-absorption by allowing water to pass through the ground substance between the cells. In an attempt to confirm Ginetzinsky's findings it became clear that his method 2 is unsuitable for quantitative assay of urinary hyaluronidase for the following reasons : (1) Precise estimation of hyaluronidase by any viscosimetric method is dependent on a constant electrolyte composition of the hyaluronidase–hyaluronic acid system, as was demonstrated in 1940 by Madinaveitia and Quibell 3 , and by McLean and Hale 4 . Urine has a variable electrolytic composition, and as Ginetzinsky does not appear to make any correction for this, his results are not quantitative. (2) Ginetzinsky 1 fails to express his results as hyaluronidase excreted per minute, relying solely on arbitrary units per ml. If hyaluronidase were excreted at a constant rate like creatinine, then a graph of its concentration against urine flow per minute would be similar to Ginetzinsky's Fig. 1. (3) He measures the initial viscosity of the mixture of urine, buffer and hyaluronic acid, the measurement being repeated after twenty minutes incubation, and the per cent reduction in viscosity is expressed as arbitrary units. This procedure is open to error as there is a rapid fall in viscosity before the initial reading 5 if a high concentration of hyaluronidase is present.