Induction of a labile chicken plasma coagulation factor by choline: dose-response relations, specificity, and effects of protein synthesis inhibitors.
Minimum oral doses of 21.5 mg/kg choline chloride were required for induction of maximum plasma level of the choline-dependent component (pi-factor) of of the labile factor activity complex in chickens on a choline-deficient diet. Several derivatives and potential precursors of choline were inactive as substitutes for the free base. After intravenous injections of optimal doses of choline, an initial lag of about 8 min was followed by a linear increase in pi-factor level reaching the maximum level about 31 min after the injection. The response was blocked and arrested by simultaneous and delayed injections, respectively, of puromycin and cycloheximide. After intravenous injections of actinomycin D, the response of choline was unaffected by a delay of up to 40 min, but completely abolished by a further delay of 90 min or more. The data suggest that the plasma level of pi-factor is goverened by the supply of choline by regulation of a pre-translational step in the biosynthesis of pi-factor.