Effect of Aureomycin on the Response of Rats to Various forms of Vitamin B6

Abstract

In agreement with earlier results, rats fed pyridoxal or pyridoxamine incorporated into the basal ration grew less than rats fed equimolar amounts of pyridoxine. The addition of vitamin B₁₂ to the basal ration did not alter the relative activities of the three forms of vitamin B₆. Aureomycin increased the growth of rats fed low levels of pyridoxine. This increase was sufficient to cause over-all errors of 10 to 100% in a bioassay for vitamin B₆, but largely disappeared when high levels of the vitamin were fed. Aureomycin caused a marked increase in the growth of rats fed limiting amounts of pyridoxal or pyridoxamine. In the presence of the antibiotic the three forms of vitamin B₆ were approximately equal in growth-promoting activity. Rats fed an assay diet containing 18% of casein and 0.4% of methionine showed linear growth responses to graded doses of vitamin B₆. No preliminary depletion period was necessary. It is postulated that aureomycin may act to prevent utilization or destruction of the growth-promoting nutrient, vitamin B₆, by intestinal microorganisms, thus increasing the amount available to the rat, and that a similar action directed toward other known and possibly unknown food factors may explain in part the growth-promoting effects of antibiotics in crude rations.