Effects of Dietary Biotin on Liver Pyruvate Carboxylase and 32P Incorporation into Nucleic Acids in Livers of Chicks

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Abstract
In chicks fed a biotin-deficient purified ration, liver pyruvate carboxylase (PC) activity gradually decreased to very low levels at 29 days of age (0.45 unit per gram), whereas in normal controls PC activity increased considerably between 9 and 16 days of age, reaching a level of 21.7 units per gram of liver, and remained relatively high until 29 days of age. Level of biotin fed affected PC activity. At levels between 0 and 80 µg/kg, there was generally only a slight increase in PC activity with increasing biotin levels, whereas increases in biotin supply between 80 and 320 µg/kg of ration resulted in a marked increase in PC activity. Increasing the level of biotin supplementation from 320 to 640 µg/kg of ration resulted in only a small increase in PC activity. The low rate of response at levels of biotin up to 80 µg/kg and the increased rate of response above 80 µg/kg suggested that usage of biotin in chicks for alternate functions might have priorities depending upon the extent of its supply. A deficiency of biotin resulted in a marked decrease in the in vivo incorporation of 33P into RNA and DNA in livers of chicks as compared to those fed an abundant amount of biotin (640 µg/kg of ration). When suboptimal levels of biotin (80 or 120 µg/kg of ration) were supplied, 32P incorporation into nucleic acids of chick liver was only slightly less than that of controls fed a high level of biotin.