Xanthine oxidase/dehydrogenase in mammary gland of mouse: relationship to mammogenesis and lactogenesisin vivoandin vitro

Abstract

SummaryXanthine oxidase/dehydrogenase (XO/XDH) increases at mid gestation in mammary gland but not in liver of the mouse and remains elevated until the pups are weaned at 20 d post partum. The increase in enzyme activity is due neither to alteration in activators or inhibitors nor to a production of a variant enzyme with altered catalytic properties. The increase is precededin vivoby a surge of prolactin-like activity (placental lactogen) in plasma, and prolactin is required for induction of XO/XDH in explant culturein vitro. Induction of XO/XDHin vivoandin vitroprecedes the full histological differentiation of the gland. In addition, induction of XO/XDHin vitrooccurs more rapidly and at lower concentrations of prolactin than does histological differentiation. Thus although XO/XDH is present in milk, increased XO/XDH activity is an early event in mammogenesisin vivoandin vitrorather than a terminal component of differentiation.