Human FSH isoforms: carbohydrate complexity as determinant of in-vitro bioactivity

Differences in sialic acid content of the hormone have been considered the main determinant or FSH polymorphism. The aim of the present study was to i nvestigate the effect of variations in the oligosaccharide structure of the intrapituitary human FSH (hFSH) glycosylation variants on their intrinsic biological activity. FSH charge isoforms obtained after chromatofocusing we re further separated lay lectin affinity chromatography [Concanavalin A (Co nA), Wheat germ agglutinin (WGA), Lentil lectin (LcH)]. Isolated isoforms w ere separately tested for in-vitro bioactivity in a rat Sertoli cell aromat ization bioassay. Our results show that: (1) FSH microheterogeneity is due not only to variations in the sialic acid content of the hormone but also t o differences in the internal structure of the carbohydrate chains, and (2) variations in the sialic acid content as well as differences in the comple xity of the glycans determine the full biological expression of FSH glycosy lation variants. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved .