Pituitary gonadotropic hormone from a chondrostean fish, starred sturgeon (Acipenser stellatus Pall.) III. Polymorphism.

Four biologically active fractions of gonadotropic hormone (aci-GTH-A, -B, -C, -D) were isolated and purified from acetonized pituitaries of the starred sturgeon (Acipenser stellatus Pall.). Their separation was achieved by DEAE-cellulose chromatography. Disc-electrophoresis and especially isoelectric focusing in polyacrylamide gel showed that each fraction contained several components. Not less than 15 different components as a whole with isoelectric points ranging from 4.5 to 7.0 could be counted in four aci-GTH preparations. All these components were active in toad oocyte maturation test. Only two of four preparations (aci-GTH-A and -D) were practically free of common components. All aci-GTH preparations were shown to be homogeneous and identical by molecular weight, sedimentation coefficient, sialic acid content, and some immunological properties. N-terminal amino acid analysis revealed tyrosine and leucine in all aci-GTH preparations, with the only exception of aci-GTH-D that contained an additional polypeptide with N-terminal glycine. No differences in the spectra of aci-GTH isoforms were found when pituitary extract, newly purified or 3 years older hormone preparations were submitted to isoelectric focusing.