Growth stimulation of BHK cells in culture by free biotin in serum

A dialysate of fetal bovine serum stimulated the growth of BHK cells in a medium containing 1% dialyzed serum. The growth-stimulating activity of the dialysate was separated in a single peak with Biogel P-2 chromatography, and a single active component was further fractionated with paper and thin-layer chromatography. The component was identified as biotin. Pure biotin behaved the same as the active component in the dialysate and had the same growth-stimulating activity. The dialysate contained only the free biotin that was present in serum. Free biotin was found in relatively large amounts in fetal (bovine and human) sera, and only a very small percentage of dialysates of adult (bovine, horse, swine, and human) sera had traces of growth-stimulating activity. The possible role of free biotin in the body is discussed.