Studies in detoxication. 35. Spectrophotometric determination of β-glucuronidase using p-chlorophenylglucuronide as substrate

537 2. After a preliminary incubation period of 45 min., i.e. after a steady state had been established, 42K in the form of 42KC1 was added to slices of guinea pig-brain cortex and to pieces of ox retina, and the rate ofmigration of 42K into the tissue was measured. From these measurements the rate of potassium exchange in the steady state was calculated. The turnover rate potassium exchanged/min. potassium present in tissue was 3-5-4 in brain cortex and 7-10 in retina.