Comparative Effectiveness of Vitamin B12, Whole Liver Substance and Extracts High in Apa Activity, as Growth Promoting Materials for Hyperthyriod Animals

Abstract

Rats fed thyroid-containing rations require for growth a factor or factors present in liver, fish soluble components and tomatoes. Skim milk and fibrin contain little or none of this factor. Highly purified liver extracts rich in the anti-pernicious anemia principle carry the factor. APA preparations had a significant effect on longevity when injected into hyperthyroid rabbits. The significance of these observations in the development of an assay for the APA factor is noted. Vitamin B₁₂ was found to be a growth factor for the hyperthyroid rat. Treatment of folic acid with good sources of the “intrinsic factor” did not result in the formation of a growth promoting substance. “Formylfolic acid” was likewise inactive in our assay. Iodinated casein may be used to produce the thyrotoxic syndrome. Exhaustive extraction of whole liver powder with 60% ethanol, 95% ethanol, 1:1 ethanol: ether or water brought only part of the active material into solution. These observations as well as others indicate the possible dual nature of the material which, in addition to the known vitamins, supports the growth of animals fed thyroxine-containing rations.