Isolation and partial characterization of LH, FSH and TSH from canine pituitary gland

A new preparative procedure without using ion-exchanger is described for the efficient purification of canine LH (cLH), FSH (cFSH) and TSH (cTSH) from the pituitary gland. The hormones were extracted from the pituitary homogenate with an ammonium sulfate solution, and were separated by Concanavalin (Con) A affinity-, hydrophobic interaction-, then immobilized metal ion affinity chromatography. In the immobilized metal ion affinity chromatography, we used copper (Cu2+) as chelated metal ion with ammonium ion gradient and pH gradient in phosphate buffer to attain separation of the hormones. High purity of cLH, cFSH and cTSH was indicated as single bands in SDS-PAGE, with apparent molecular masses of 34, 36 and 37 kDA, respectively. The purified hormones showed two bands corresponding to alpha (20 kDa) and beta subunits (cLH beta: 16 kDa, cFSH beta: 22 kDa, cTSH beta: 16 kDa) under reducing condition in SDS-PAGE. The purified hormones were prepared in good recovery (LH: 53%, FSH: 34%, TSH: 36%) with high biological activity or binding activity to the receptor. Cross-contamination of the purified hormone was less than 0.5%. Examination of the hormone fraction with isoelectric focusing showed that major peaks of isoelectric isoforms were maintained throughout the purification steps of cLH and cFSH, while a few peaks were lost in Con A affinity chromatography in cTSH purification. It was concluded that the present method could prepare highly purified cLH, cFSH and cTSH which retained isoforms of the hormones and biological activity or binding affinity to the receptor.