The experimental production of vitamin B12deficiency in the baboon (Papio cynocephalus). A 2-year study

Abstract

1. The development of vitamin B12deficiency, as indicated by the serum and liver vitamin B12levels and the excretion of methylmalonic acid, was studied over a 2-year period in baboons (Papio cynocephalus) given a diet deficient in vitamin B12. The effects of partial hepatectomy and the inclusion of either ampicillin or sodium propionate in the diet on the rate of development of the deficiency were also studied.2. The baboons had previously been fed on a mainly vegetarian diet. Their serum vitamin B12levels were less than 100 ng/l and the mean liver vitamin B12concentration was 0·56 μ/g. Similar serum and liver vitamin B12levels were found in baboons given a purified diet supplemented with 1 μg vitamin B12/d, and marked increases in the serum and liver vitamin B12levels occurred when the daily intake was increased to 2 μg.3. The serum vitamin B12levels decreased to less than 20 ng/l in all baboons given a vitamin B12-deficient diet.4. The liver vitamin B12concentration also decreased in all baboons given a deficient diet. At 9 months the lowest levels (0·20 μ/g) were found in partially hepatectomized baboons but subsequently baboons given the diet containing ampicillin had the lowest levels (0·11 μ/g).5. The excretion of methylmalonic acid after a valine load was found to be inversely related to the liver vitamin B12concentration. In the early part of the study, partially hepatectomized baboons excreted the highest amount but subsequently baboons given a diet containing ampicillin excreted the highest amount.6. Increased formiminoglutamic acid excretion after a histidine load was observed in two baboons given a vitamin B12-deficient diet and in both baboons the liver folic acid concentration was low.7. No haematological or neurological symptoms of the vitamin B12deficiency were observed.