COBALT-VITAMIN-B-12 INTERRELATIONSHIPS IN LIVER OF FETUSES AND INFANTS

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. leichmannii, 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.