Purification and partial characterization of inhibin from porcine follicular fluid

Inhibin, a protein of gonadal origin that suppresses the basal secretion of follicle stimulating hormone by anterior pituitary cells has been purified from porcine follicular fluid. Using several RP-HPLC steps and gel filtration under denaturing conditions, we obtained a fraction approximately ten thousand fold purified which showed one band on SDS PAGE and in the same experiment two bands after reduction (MW ca 14K and ca 18K) suggesting a molecular weight of 32K for inhibin. Edman degradation of isolated inhibin and carboxymethylated chain A indicated that the first 6 residues were H-Ser-Thr-Ala-Pro-Leu-Pro-; by subtraction, the first 3 residues of chain B could be deduced to be H-Gly-Leu-Glu-. EC50 was ca 0.3 ng/ml or 10 pM in our in vitro pituitary cell culture assay. Antibodies to residues 1-6 were raised which could immunoneutralize purified inhibin activity in an in vitro assay.