Serum ferritin concentration and other iron-related blood characteristics of Holstein dairy bulls were studied. Serum ferritin concentration was measured by a two-site immunoradiometric assay (2-site IRMA). The mean value ±standard error of this protein in blood serum of dairy bulls reared in breeding stations near to Sapporo was 36±7 ng/ml in adult (n=109) and 13±1 ng/ml in young bulls (n=19), respectively. Similar changes with age were observed in mean corpuscular volume, mean corpuscular hemoglobin, hemoglobin concentration, hematocrit, total serum protein and transferrin concentration. On the other hand, count of red blood cells in young bulls was higher than that in adult ones. But sexual difference in serum ferritin concentrations was not detected between bulls and cows previously reported. Furthermore, the ferritin levels in adult bulls were also measured by an enzyme immunoassay (EIA) used horseradish peroxidase as an enzyme and ABTS as a substrate. A correlation coefficient between ferritin concentrations determined by two methods was a significant high value (r=0.990). However, in the present EIA of serum ferritin, determination of low ferritin level below 5 ng/ml was likely difficult. But this assay system may be useful to determine high serum levels of ferritin in some metabolic disorders of animals.
An experiment was conducted with 56 piglets to investigate the absorptive phase of iron during the developing period of the intestine using ligated segments in vivo. Iron-untreated animals were studied at birth, 24 to 36, 72 to 84, 120 to 132 and 168 to 180 hr after the first nursing, whereas treated animals were used at 168 to 180 hr after the first nursing. 5 9Fe-labeled ferric citrate with a molecular weight of 1,500 was applied to prevent pinocytosis activity from influencing intestinal absorption for iron. The newborn pig intestine exhibited an active absorption for iron, which was maintained throughout this age-range. The duodenum was the principal site of iron absorption by the neonatal intestine. Iron transfer from lumen to carcass did not coincide with the changes associated with protein absorption taking place in the pig intestinal mucosa during the neonatal period. Iron treatment depressed 5 9Fe uptake of intestinal segments. Accordingly, it seems likely that the iron absorptive system is fully functional at birth and that an active absorption for iron in the neonates is not due to intestinal capacity of pinocytosis. Although mucosal uptake of 5 9Fe was reduced markedly with advanced age, no significant differences were found between sites of mucosal uptake of 5 9Fe. Mucosal uptake of 5 9 Fe did not correlate with 5 9 Fe transfer from lumen to carcass. In newborn pigs' jejunum and ileum, mucosal uptake of 5 9Fe was relatively high as compared with net transport from lumen to carcass. Iron treatment had no effect on mucosal uptake of 5 9Fe. Thus, it seems likely that great iron demand due to a rapid increase in the body mass causes reduced iron content in mucosal cell and an active absorption for iron. Similarly, it is possible that the surface of the mucosal cell of the newborn piglets regulates iron transfer from lumen to carcass.
An experiment was conducted with 38 piglets to clarify relationships ofhepatic xanthine oxidase and plasma ferroxidase to storage iron mobilization. In conjunc-tion with the result of hypotransferremia, hepatic xanthine oxidase and plasma ferroxidasewere extremely low at birth. Accordingly, it seems likely that due to these enzymatic andprotein deficits, the rate of iron storage cells to plasma iron transfer may be quite limited, if at all. When there were sudden increases in plasma transferrin, ferroxidase activity andhepatic xanthine oxidase after piglets had utilized colostrum, a corresponding increase iniron release from the liver was observed. It is possible that the ferrous to ferric cycles inthe liver and plasma are activated by the increase in iron-releasing enzymes and plasmatransferrin, and that thereafter the rate of transport of iron from storage cell to erythro-poietic organ is accelerated still more.Eventually, as a result of storage iron depletion, plasma iron and hemoglobin levelsdecreased and overt iron deficiency appeared markedly from 3 days of age onward.. Milkferroxidase and transferrin showed a high level at farrowing and decreased progressivelyto 10 days postpartum. Although plasma ferroxidase increased intensively after pigletshad absorbed colostrum, the amount of colostral ferroxidase absorbed by piglets was verysmall, as compared with that derived from endogenous sources after the cessation of theabsorption of colostral protein by the piglets.
