Purification and characterization of testicular transferrin secreted by rat Sertoli cells

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Abstract
Sertoli cells synthesize and secrete a transferrin-like protein (testicular transferrin). The testicular transferrin was analyzed and compared with serum transferrin. Testicular transferrin was obtained from the medium of cultured rat Sertoli cells, whereas serum transferrin was obtained from rat serum. Both proteins were purified with the use of phenyl-Sepharose hydrophobic chromatography and transferrin immunoaffinity chromatography. The purified proteins had similar molecular masses (75,000 Da) and amino acid compositions. The pattern of tryptic peptides from testicular and serum transferrin were essentially the same when analyzed by reverse-phase high-pressure liquid chromatography. The carbohydrate composition of both transferrins was determined by several colorimetric assays and GLC. Testicular transferrin, isolated from cell culture medium, had increased amounts of glucose, galactose and glucosamine. Serum transferrin that was incubated with cell culture medium also had a large amount of associated glucose. Testicular transferrin and serum transferrin evidently are structurally very similar and are possibly products of the same gene expressed in 2 different tissues, the testis and liver. The amount of carbohydrate associated with these 2 proteins is different.