Biological characterization of the isoforms of urinary human follicle-stimulating hormone contained in a purified commercial preparation.

The main physicochemical and biological properties of the several isoforms of urinary follicle-stimulating hormone (uFSH) present in a commercially available uFSH preparation were analysed. Purified urinary FSH was submitted to chromatofocusing and several immunoactive forms of uFSH with isoelectric points (pI) ranging from 5.5 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 uFSH isoform or pool of neighbouring isoforms (pI value 5.5-5.1, pool I, 3.8 +/- 1.0% of total immunoactivity recovered; pI value 5.0-4.6, pool II, 18.4 +/- 3.6% of total; pI value 4.5-4.3, pool III, 14.9 +/- 1.5% of total; pI value 4.1, pool IV, 8.2 +/- 1.4% of total; salt peak, pool V, 51.1 +/- 6.4% of total) eluted as single FSH peaks after Sephadex G-100 exclusion chromatography (apparent M(r) 60,000). Even though FSH 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 uFSH isoform tested; starting from a pI value of 5.5, the receptor binding activity of FSH decreased from 5.9 +/- 0.39 to 2.4 +/- 0.19, 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)