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Background:The clinical significance of the increased concentrations of cardiac troponins observed in patients with end stage renal disease (ESRD) in the absence of an acute coronary syndrome (ACS) is controversial. One proposed explanation is that immunoreactive fragments of cardiac troponin T (cTnT) accumulate in ESRD. We used gel-filtration chromatography (GFC) to ascertain whether fragments of cTnT, which could cross-react in the commercial diagnostic immunoassay (Roche Diagnostics), were the cause of the increased cTnT in the serum of patients with ESRD. Methods: We subjected sera from ESRD patients (n ‫؍‬ 21) receiving dialysis and having increased cTnT concentrations to size-separation GFC. We detected cTnT in the chromatography fractions by use of the same antibodies used in the commercial assay for serum cTnT. Results: In all patients, cTnT immunoreactivity eluted as a major, homogeneous peak in an identical position between the peaks of serum prolactin [relative molecular mass (M r ) 23 000] and albumin (M r 67 000): the elution pattern of cTnT in samples obtained from ACS patients was identical to that of the ESRD patients. There was no evidence that low-molecular-mass (M r <23 000) cTnT fragments were the cause of the increased cTnT in the patients studied. Conclusions: The form of cTnT observed in the serum of patients with kidney failure and immunoreactive in the diagnostic assay is predominantly the free intact form, as in patients with ACS. Our data are consistent

Milk is an attractive vehicle for introducing iron supplements into iron-deficient infants and children. This study compares the effects of milk and caseins on the whole-body absorption of radioactive iron complexes in an attempt to resolve the controversy over whether milk and its constituent phosphoproteins seriously impair iron absorption. Evidence is presented to clarify the role of the calcium-casein micelles of cow's milk in binding iron donated by the ferric-nitrilotriacetate (NTA) complex. The absorption of iron from isolated Fe(III)-casein complexes was studied in mice as a function of the casein--to--Fe ratio and was compared with the absorption of Fe(III)-NTA at equivalent levels. Even at casein--to--Fe ratios higher than those found in conventional iron-supplemented cow's milk (10-15 mg Fe/qt; casein P:Fe congruent to 34), absorption of iron(III) from the casein or NTA complex was not significantly different. There was no significant difference in the absorption of iron administered to mice and chicks as ferrous ion, ferric-NTA, or ferric fructose; nonfat cow's milk did not inhibit the absorption of these iron compounds. For the chick, in fact, milk significantly enhanced the absorption of iron from the ferric-NTA chelate. In order to affect iron absorption significantly casein would have to be present considerably in excess of that found in conventionally supplemented cow's milk.