Essential metal balance and retention during the second half of pregnancy in the rat.

The daily copper, zinc, iron, magnesium, calcium, sodium and potassium retention from the diet in rats during the second half of pregnancy have been determined and compared with those of adult virgin male and female rats. Pregnant rats had higher mean magnesium and potassium daily retentions than virgin females. The retention of essential metals changed along the second half of pregnancy towards lower values for copper and magnesium and higher ones for potassium. The net absolute metal retention followed the same trends. All other metals studied showed little global differences versus controls without clearly identifiable trends. The results suggest that metal retention is an adaptative element in maintaining the pregnant rat's metal supply, as the considerable metal retention in the first half of pregnancy is modulated in the second half according to the actual needs of the maternofetal unit.