The effects of pregnancy and lactation on copper and zinc retention in the rat.

1. The accretion of copper and zinc in maternal tissues, conception products and postnatal offspring of the rat was determined at different stages of pregnancy and lactation. 2. Equations relating the weight of the bodies of the developing young and of the amounts of Cu and Zn in them to the time that has elapsed since conception showed that, early in pregnancy, the specific rates of accretion of Cu or Zn were greater than that of weight, but declined more rapidly as development continued. The instantaneous rates of accretion of both metals rose throughout pregnancy but only that of Cu continued to increase during lactation. 3. The amount of Cu in the maternal body rose significantly during pregnancy and declined thereafter, but relatively small changes in its Zn content occurred. 4. The results are discussed in relation to the relative demands for these metals during pregnancy and lactation.