Short-term zinc kinetics in pregnant rats fed marginal zinc diets

The effect of pregnancy and a chronic, marginal intake of zinc on zinc kine tics was studied in rats. Weanling female rats were fed either a zinc-adequ ate diet, containing 30 mu g Zn/g, (30Zn) (n = 16) or a marginally zinc-def icient diet, containing 6 mu g Zn/g, (6Zn) (n = 16). After 6 wk, half of ea ch group was mated (30ZnPG, 6ZnPG). A third group of pregnant rats was pair -fed (PFPG) (n = 6) to the 6ZnPG group. On d 20 of gestation, or at the end of the 9-wk study, Zn-65 was injected intravenously. The plasma 65Zn disap pearance curve over the next 105 min was used to study the size and fractio nal turnover rates of two rapidly exchanging zinc metabolic pools (pool a a nd pool b). Plasma zinc concentrations on d 20 of gestation were significan tly lower in the 6ZnPG group compared with the 30ZnPG and PFPG controls, (P < 0.05). The exchangeable pools were also smaller in the 6ZnPG group compa red with the 30ZnPg and PFPG groups, (P < 0.02); this reduction was accompa nied by a 60% greater fractional turnover rate of pool a, (P < 0.02). Pregn ancy outcomes did not differ among the three groups. We conclude that there is an increase in the turnover rate of the exchangeable plasma zinc pool w hen dietary zinc intake is marginal during pregnancy. This response may hel p maintain a supply of zinc to the growing fetus when plasma zinc concentra tions are reduced.