The transport of vitamin A in rat serum with special reference to the occurrence of unidentified metabolites of vitamin A in the rat

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Abstract
With the aid of [2-C14]vitamin A it was established that vitamin A alcohol is transported in rat serum in association with the a1-globulin. The vitamin A alcohol is not associated with the lipo-proteins. When a borate-phosphate buffer is employed for the electrophoretic fractionation of rat-serum proteins, the mobility of the a1-glycoprotein is greater than that of the albumin. By employing veronal buffer and borate-phosphate buffer for the electrophoretic fractionation of rat-serum proteins, it could be concluded that vitamin A alcohol is probably also not associated with the [alpha]1-glycoprotein. A labelled component(s) derived from [2-C14]-vitamin A and associated with the [alpha]2-globulin can occur in serum and most likely is a normal constituent of serum, occurring in a concentration equivalent to 20-30 International Units of vitamin A. It has not been possible as yet to establish whether these derivatives of vitamin A are active intermediates or degradation products. On giving [2-C14] vitamin A orally to vitamin A-depleted rats, 7-12% of the radioactivity is excreted in the urine within 48 hr. after administration.