Reduction of plasma urate levels in the cockerel with polyethylene glycol-uricase

Uricase from C. utilis and uricase to which polyethylene glycol had been attached were injected into leghorn cockerels in an attempt to lower plasma urate levels. Twenty units of either enzyme reduced urate levels to near zero for 24 hr on initial injection, whereas 10 U were effective for less than 6 hr. After injection with four-weekly doses of enzyme, unmodified uricase was ineffective in lowering plasma urate levels. Polyethylene glycol-uricase, however, was as effective as on the first injection. Both enzyme preparations appear in the lymph shortly after injection into the rat, although polyethylene glycol-uricase appears slightly sooner and maintains a more constant level than uricase.