Cobalt-vitamin B-12 interrelationships in liver of fetuses and infants

Abstract

The concentrations of cobalt and vitamin B-12 were measured in 90 autopsy samples of liver from fetuses and newborn infants from the city of Brasilia, Brazil. Gestational age varied from 19–42 weeks. Vitamin B-12 was assayed by L. Ieichmannii, and cobalt by electrothermal atomic absorption spectrophotometry. Concentrations on a wet weight basis of vitamin B-12 ranged from 83–758 ng/g of liver (293.15 + 14.91; mean + SEM), and of cobalt ranged from 6–45 ng/g liver (17.68 ± 0.85; mean ± SEM). The percentage of cobalt as vitamin B-12 ranged from 23–100 (72.4 ± 1.8; mean ± SEM). The percentage of cobalt as vitamin B-12 was not affected by fetal development measured as liver weight ( r = 0.08; P < 0.4). Liver weight was not significantly correlated with concentrations of either cobalt ( r = −0.16; P < 0.14) or vitamin B-12 ( r = −0.15; P < 0.14). However, the correlation between cobalt and vitamin B-12 concentrations was highly significant ( r = 0.83; P < 0.0001). Concentration of vitamin B-12 can be derived from cobalt concentration by the equation [vitamin B-12] = 14.62x[Co] + 34.48.