Abstract
SUMMARY: The effect of prolactin on the activity of β-glucuronidase in the testis of the rat and mouse has been studied in vitro. Prolactin increased this activity, and a linear log dose-response relationship was found to exist with doses of between 0·3 and 1·2 mg. of a preparation of prolactin containing between 20 and 25 i.u./mg. The optimal conditions for this effect have been investigated. Twenty other substances have been tested; none increased the enzymic activity, but six decreased it. Possible mechanisms for this effect are discussed.