The unsaturated vitamin B12 binding capacity (UBBC) of serum, the three transcobalamins (TC I, TC II, TC III) and serum cobalamin have been studied in adult sickle cell patients with Hb SS. An increase in the level of the binding capacities of TC I and TC III resulting in an increase in UBBC was observed in these patients. There was no difference in the level of the binding capacity of TC II, while there was a significant reduction in the level of serum cobalamin. These changes in the pattern of these binding proteins are discussed in relation to the changes of these binding proteins in paediatric sickle cell patients with Hb SS. The results indicate that the pattern of these binding proteins changes with age among sickle cell patients resulting in an increased level of the binding capacities of TC I and TC III. These increases lend support to the view that these two similar binding proteins are involved in the defence mechanism of the body.

Male weanling wistar rats were fed either a vitamin B(12)-deficient diet or a vitamin B(12)-deficient diet supplemented with DL-homocysteine for 12 weeks. The control group was given a vitamin B(12)-supplemented diet for 12 weeks. Hepatic folate, hepatic 5,10-methylene THF reductase (EC 1.1.1.68) and hepatic 5-methyl THF; homocysteine- methyl transferase (EC 2.1.1.13) activities were assayed in all the rats after killing. The hepatic folate activity was very low among the homocysteine-supplemented rats. 5,10-methylene THF reductase and 5-methyl THF; homocysteine methyl transferase activities were increased in the homocysteine-fed rats. These results show that dietary DL-homocysteine has some regulatory effect on the two enzymes involved in the production of ‘free’ THF.