Radiochromium distribution during saline diuresis

Chromium metabolism. A literature review

The trivalent state of chromium (Cr3+) is that encountered in biological milieus and is responsible for its nutritional activity. The principal route by which trivalent chromium enters the body is the digestive system. Chromium in foods is present both in the inorganic form and as organic complexes. Intestinal absorption of chromium is low (0.5-2%), and the mechanism has not yet been fully elucidated. Absorbed chromium circulates as free Cr3+, as Cr3+ bound to transferrin or other plasma proteins, or as complexes, such as glucose tolerance factor (GTF)-Cr. Circulating trivalent chromium can be taken up by tissues, and its distribution in the body depends on the species, age, and chemical form. It is excreted primarily in the urine by glomerular filtration or bound to a low-mol-wt organic transporter. Chromium metabolism is still imperfectly understood. The use of 51Cr has nevertheless furnished valuable data concerning its transport and excretion.

Energy production, intracellular amino acid pools, and protein synthesis in chronic renal disease

Intracellular glycolytic regulating enzyme activities, pyruvate kinase (PK) and phosphofructokinase (PFK), adenylate kinase (AK), energy charge (Ech), free amino acids (ICAA), and protein synthesis (PS) were measured in polymorphonuclear leukocytes--used as a cell model--in 62 adults and 12 children with chronic renal failure, and 66 normal adults and 21 children as comparison controls. In normal subjects, children had significantly lower enzyme activities and cell amino acid levels but similar Ech and higher PS than adults. ICAA concentrations were significantly higher than plasma amino acid concentrations (PAA) in both groups, and the PAA were not correlated with, nor indicative of, the ICAA concentrations. The variance (R2) in PS could be largely accounted for by a combination ("set") of six ICAA, as determined by multivariate analysis. The sets differed in children vs adults, suggesting that different proteins were being synthesized. In the uremic patients, reduced PF, PFK, Ech, most ICAAs and PS were indicative of cellular malnutrition. For the uremic adults, the abnormalities in cell metabolism were modified by therapy--nondialyzed uremics being worst, CAPD patients best and approximately normal, and hemodialyzed intermediate. The uremic CAPD children had reduced, PK, PFK, AK, most ICAA, and PS. Ech was increased. Cellular malnutrition in children with chronic renal failure may contribute to their poor growth.