Essential Metal Balance and Retention during the Second Half of Pregnancy in the Rat

Abstract

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.

Combined Pregnancy and Starvation Effects on Rat Tissue Iron, Zinc and Copper Contents

“…This differ ent behavior compared with that on the 19th day seems to be related to the newly gained ability of the fetus to mobilize its own re serves as well as to a more intense hold-up of fetal growth [25], The fetal copper homeosta sis is not deeply altered, in a way comparable to that of energetic substrates [22], The strat egy followed by the pregnant rat in iron dis tribution differs very much from that de scribed for copper [26], The maternal iron reserves are highly affected by pregnancy [10], thus establishing a close dependence on dietary iron for fetoplacental supply. In ad dition, iron is not absorbed with higher effi ciency during pregnancy [21 ]. When the data presented are computed for the whole ani mal, the pattern observed suggests a close relationship with weight gains and losses.…”

“…It can be assumed that increased food intake and copper absorption [6,21] should be of critical importance for the accumula tion of copper in the materno-fetal unit [22]. A high copper absorption from the diet has been reported in the rat in mid-gestation [6].…”

“…There was a close equilibrium between zinc intake and fetal zinc needs [21], as neither the increased food intake [3], nor the described higher zinc intestinal absorptive capability [5,27] observed during pregnancy resulted in increased maternal zinc stores [11], Di etary zinc deficiencies resulted in mobiliza tion of maternal bone zinc [28] and even in teratogenic effects [29] when the fetal needs were not adequately fulfilled [28], The levels of zinc described are in agreement with pre vious reports [10] pointing towards a de crease in tissue zinc stores during pregnancy, which coincides with the postulated pattern of mobilization of this metal for distribution and transfer to the fetuses. Starvation results in a decrease of tissue zinc, most remarkable on the 21st day; when the data are computed for the whole animal, this decrease is en hanced.…”

“…The homeostasis of copper, iron and zinc in short-term starved pregnant rats can be defined as part of the 'accelerated starvation' pattern observed for energetics substrates [20,21 ]. This is so despite their different dis tribution and transfer strategies, as well as their sensitivity to dietary alterations.…”