A Serum Fraction with “Sulfation Factor Activity” Stimulates in Vitro Incorporation of Leucine and Sulfate Into Protein-Polysaccharide Complexes, Uridine Into RNA, and Thymidine Into DNA of Costal Cartilage from Hypophysectomized Rats

A serum fraction which contains the so-called sulfation factor activity was found to stimulate in vitro incorporation of either (UC) or (³H) leucine and (³⁵S) sulfate into proteinpolysaccharide complexes (PP), (³H) uridine into RNA, and (³H) thymidine into DNA of costal cartilage from hypophysectomized rats. Tissue was incubated in a medium containing 14 amino acids and glucose. The serum fraction consistently increased incorporation of leucine into protein of PP prior to the increase of sulfate incorporation into polysaccharide of PP. Stimulation of uridine incorporation into RNA did not necessarily precede stimulation of leucine incorporation into protein of PP, and the former could be profoundly inhibited with actinomycin without seriously affecting the latter. In experiments of 4 hr duration or less actinomycin inhibited incorporation of uridine into RNA≫leucine into protein of PP>sulfate into polysaccharide of PP. Stimulation of thymidine incorporation into DNA by the serum fraction occurred later than the other effects, requiring 6–10 hr for detection but reaching a remarkable level by 24 hr. (Endocrinology86: 721, 1970)