Bovine follitropin: Isolation and characterization of the native hormone and its α and β subunits

1. A reproducible procedure was developed for the purification of bovine follitropin.
2. The methode involved ammonium sulfate precipitation, ion exchange and adsorption chromatography, concanavaline-A-Sepharose chromatography and gel filtration.
3. A specific radioligand receptor assay was used to monitor each chromatographical step.
4. The potency of highly purified bovine follitropin as measured by Steelman and Pohley bioassay was 62 times the NIH-FSH-B1 standard preparation.
5. Contaminations of bovine follitropin by other glycoprotein hormones such as thyrotropin and lutropin amounted to 3 and 0.45 per cent by weight respectively as measured by specific radioimmunoassays and radioligand receptor assays.
6. The subunits alpha and beta of bovine follitropin were obtained by incubation in acidic urea, the chains being then separated by anion exchange chromatography. The subunits were submitted to complete characterization. The amino terminal residue of the alpha subunit is phenylalanine while a half cystine residue was found at the amino-terminal end of the beta chain.
8. Cross-contamination of the alpha and beta subunit preparations was measured by specific radioimmunoassays and amounted to 0.02 and 0.1 per cent by weight respectively.