Biological characterization of the naturally occurring analogues of intrapituitary human follicle-stimulating hormone.

In the present studies we analysed the main physicochemical and biological properties of the several isoforms of human pituitary follicle-stimulating hormone (hFSH). Extracts of total anterior pituitary glycoproteins from adult donors were submitted to chromatofocusing and several forms of immunoactive hFSH with isoelectric points (pI) ranging from 7.6 to 3.8 were identified. An additional isoform was detected after passing through the chromatofocusing column a 1.0 M NaCl solution (salt peak). Each hFSH isoform or pool of neighbouring isoforms (pI value 7.6-7.1, pool I, 1.5 +/- 0.13% of total immunoactivity recovered; pI value 5.9-5.3, pool II, 8.9 +/- 1.6% of total; pI value 5.0-4.7, pool III, 14.4 +/- 1.4% of total; pI value 4.5-4.1, pool IV, 54.8 +/- 4.9% of total; pI value 3.9-3.8, pool V, 3.67 +/- 0.9% of total; salt peak, pool VI, 16.8 +/- 4.8% of total) eluted as single hFSH peaks after Sephadex G-100 exclusion chromatography (apparent Mr 60,000). Even though hFSH present within each pool was recognized by a receptor preparation, the receptor-binding activity expressed as the radioreceptor assay:radioimmunoassay (RRA/RIA) activity ratio varied with the pI value of the particular hFSH isoform tested; starting from a pI value of 5.9, the receptor-binding activity of hFSH decreased from 4.25 +/- 0.28 to 1.17 +/- 0.14, as the pI value of the corresponding isoform declined. A similar trend was observed when the potency of each isoform was assessed by an in vitro bioassay.(ABSTRACT TRUNCATED AT 250 WORDS)