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)
FSH is produced and secreted from the anterior pituitary gland of rats in multiple molecular forms. At times of high gonadotrophin-releasing hormone (GnRH) and oestrogen output (e.g. the morning of the day of pro-oestrus) the pituitary increases the production of FSH isoforms with isoelectric point (pI) values greater than 5.0, whilst sex steroid deprivation leads to the production of strongly acidic and less in-vitro biologically active FSH molecules. It is not known, however, whether sex steroids modulate the production of specific FSH isoforms by a direct action at the pituitary level or indirectly through altering the rate of synthesis and/or secretion of GnRH. In order to obtain some insight on this issue, we examined the charge heterogeneity of FSH secreted by cultured pituitary cells exposed to different FSH-releasing factors, oestradiol-17 beta and progesterone, alone or in different time-sequenced combinations. Anterior pituitary glands from 21-day-old female rats were enzymatically dispersed into a single cell suspension and cultured for 5 days. During days 1 to 3, cells were incubated in the absence of factors or steroid hormones; on days 3 to 4, cells were incubated in the absence (controls) or presence of either oestradiol-17 beta (3.67 nmol/l) or oestradiol-17 beta plus progesterone (3.67 and 31.8 nmol/l respectively). Finally, during days 4 to 6, GnRH (10 nmol/l) or recombinant human activin-A (2 nmol/l) were added to half of all culture wells. Media from each cell group were concentrated and the several forms of secreted FSH were then separated by polyacrylamide gel isoelectric focusing (pH range 6.5-4.0) and quantitated. All media concentrates contained several forms of immunoactive secreted FSH focusing within a pH range of 6.44-4.23. A large amount (51-76%) of total FSH recovered focused within a pI range of 4.9-4.0 (area 3), whilst 20-43% and 4-8% of the total were identified within pI range of 5.9-5.0 (area 2) and 6.5-6.0 (area 1) respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
In the present study, we investigated the biological characteristics of different molecular forms of chorionic gonadotrophin (HCG) secreted by the human cytotrophoblast during its morphological and functional differentiation in culture. Highly purified cytotrophoblasts were prepared from term placentae and cultured for 24 to 96 h in the absence or presence of 8-bromo-3',5'-cAMP. Media were collected at 24 h intervals and the secreted isoforms of HCG were then separated by polyacrylamide gel isoelectric focusing (pH range 8.0-3.0) and quantified by radioimmunoassay. The secretion of HCG was significantly increased by 8-bromo-cAMP (from 23.5 +/- 6.3 ng/ml at 24 h to 1619 +/- 835.8 ng/ml at 96 h; controls, 9.3 +/- 0.1 ng/ml at 24 h and 26.6 +/- 3.5 ng/ml at 96 h, mean +/- SD). Analysis of media concentrates from cAMP-stimulated cultures by isoelectric focusing revealed the presence of several distinct peaks of HCG within the pH range of 7.3-4.8; major peaks consistently exhibited isoelectric points (pI) of 7.3-7.0 (peak 1), 5.6-5.4 (peak 2) and 5.1-4.8 (peak 3). The relative HCG content of the most acidic peak (as % of total on gel) progressively increased with time of exposure to the cAMP analogue (from 19.8 +/- 1.6% at 24 h to 34.4 +/- 4.3% at 96 h, mean +/- SEM, P less than 0.01). HCG recovered from peak 1 exhibited the highest receptor-binding capacity and in-vitro biological potency.(ABSTRACT TRUNCATED AT 250 WORDS)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.