Measurement of zinc flux through plasma in normal and endotoxin-stressed pigs and the effects of Zn supplementation during stress

The rates of transport of zinc through plasma have been investigated in normal and endotoxin-stressed pigs. 2.65Zn added to porcine plasma in vitro rapidly equilibrated with the Zn originally present. 3. 65 Zn bound to albumin and injected intravascularly into pigs rapidly equilibrated with two kinetically distinguishable pools. The first of these pools was mainly associated with the plasma but was significantly larger than the plasma volume and substantially so in Zn-deficient pigs. The second pool appeared to represent a summation of the rapidly-exchangeable Zn within the extravascular tissues. 4. In non-stressed animals, the flux of Zn from the plasma of Zn-deficient pigs was only half that in Zn-supplemented animals. 5. Administration of endotoxin reduced the plasma Zn concentration of Zn-supplemented pigs but not of Zn-deficient animals. The fractional turnover rates of Zn were not altered in eight of the two pools following endotoxin. 6. At 10 h after giving endotoxin neither the Zn content of the two pools nor the flux of Zn through them differed significantly between Zn-deficient and control pigs. 7. Intravascular infusion of Zn at the rate which essentially prevented the usual depression in plasma Zn concentration following endotoxin failed to alleviate the effects of endotoxin on Zn-supplemented pits. 8. The reduction in plasma Zn concentration following endotoxin stress appears to be a normal physiological response which is not indicative of an increased metabolic requirement for Zn.