Purification and partial characterization of isoforms of luteinizing hormone from the chicken pituitary gland

Isoforms of chicken luteinizing hormone (cLH) were isolated from chicken pituitaries by differential extraction, sequential chromatography on HPLC cation- and anion-exchange columns, and gel-filtration chromatography. Three purified isoforms of the cLH had high biological potency in the chicken granulosa cell LH bioassay (4.21-7.4 x NIH-LH-S1 U/mg). One cLH isoform without detectable biological activity showed substantial immunological activity in a homologous cLH radioimmunoassay. The cLH isoforms contained negligible follicle-stimulating hormone activity, but some contained thyroid-stimulating hormone activity. The apparent molecular weight of cLH was 37,000 Da, and the holoprotein consisted of subunits with a molecular weight of approximately 17,000 Da.