Differential secretion of O-glycosylated gonadotropin α-subunit and luteinizing hormone (LH) in the presence of LH-releasing hormone

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Abstract

The pituitary hormones LH, FSH, and TSH are secreted as dimers of two subunits, α and β. The α-subunit, identical in all three hormones, is produced by the pituitary in excess of β and secreted as free subunit. Bovine free α does not combine with purified β-subunit and contains an extra O-linked oligosaccharide not found on dimer α. We have developed an assay to quantitate this modified form of α in the medium of incubated steer pituitary slices. The assay, based on reverse phase HPLC analysis of radiolabeled α-subunit tryptic peptides, shows that under basal conditions, 75% of secreted free α is O-glycosylated. When the secretagogue LHRH is added to the slices, a 14-fold increase in LH dimer release is observed, but secretion of the modified α is increased by only 2-fold. Our results indicate that the majority of free α-subunit secreted by the pituitary contains O-linked oligosaccharide, and that secretion of this form of α differs from that of LH dimer.

Original languageEnglish (US)
Pages (from-to)1699-1706
Number of pages8
JournalEndocrinology
Volume117
Issue number4
StatePublished - 1985
Externally publishedYes

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Luteinizing Hormone
Gonadotropins
Gonadotropin-Releasing Hormone
Oligosaccharides
Pituitary Hormones
High Pressure Liquid Chromatography
Hormones
Peptides

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

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title = "Differential secretion of O-glycosylated gonadotropin α-subunit and luteinizing hormone (LH) in the presence of LH-releasing hormone",
abstract = "The pituitary hormones LH, FSH, and TSH are secreted as dimers of two subunits, α and β. The α-subunit, identical in all three hormones, is produced by the pituitary in excess of β and secreted as free subunit. Bovine free α does not combine with purified β-subunit and contains an extra O-linked oligosaccharide not found on dimer α. We have developed an assay to quantitate this modified form of α in the medium of incubated steer pituitary slices. The assay, based on reverse phase HPLC analysis of radiolabeled α-subunit tryptic peptides, shows that under basal conditions, 75{\%} of secreted free α is O-glycosylated. When the secretagogue LHRH is added to the slices, a 14-fold increase in LH dimer release is observed, but secretion of the modified α is increased by only 2-fold. Our results indicate that the majority of free α-subunit secreted by the pituitary contains O-linked oligosaccharide, and that secretion of this form of α differs from that of LH dimer.",
author = "Christopher Corless and I. Boime",
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language = "English (US)",
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journal = "Endocrinology",
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TY - JOUR

T1 - Differential secretion of O-glycosylated gonadotropin α-subunit and luteinizing hormone (LH) in the presence of LH-releasing hormone

AU - Corless, Christopher

AU - Boime, I.

PY - 1985

Y1 - 1985

N2 - The pituitary hormones LH, FSH, and TSH are secreted as dimers of two subunits, α and β. The α-subunit, identical in all three hormones, is produced by the pituitary in excess of β and secreted as free subunit. Bovine free α does not combine with purified β-subunit and contains an extra O-linked oligosaccharide not found on dimer α. We have developed an assay to quantitate this modified form of α in the medium of incubated steer pituitary slices. The assay, based on reverse phase HPLC analysis of radiolabeled α-subunit tryptic peptides, shows that under basal conditions, 75% of secreted free α is O-glycosylated. When the secretagogue LHRH is added to the slices, a 14-fold increase in LH dimer release is observed, but secretion of the modified α is increased by only 2-fold. Our results indicate that the majority of free α-subunit secreted by the pituitary contains O-linked oligosaccharide, and that secretion of this form of α differs from that of LH dimer.

AB - The pituitary hormones LH, FSH, and TSH are secreted as dimers of two subunits, α and β. The α-subunit, identical in all three hormones, is produced by the pituitary in excess of β and secreted as free subunit. Bovine free α does not combine with purified β-subunit and contains an extra O-linked oligosaccharide not found on dimer α. We have developed an assay to quantitate this modified form of α in the medium of incubated steer pituitary slices. The assay, based on reverse phase HPLC analysis of radiolabeled α-subunit tryptic peptides, shows that under basal conditions, 75% of secreted free α is O-glycosylated. When the secretagogue LHRH is added to the slices, a 14-fold increase in LH dimer release is observed, but secretion of the modified α is increased by only 2-fold. Our results indicate that the majority of free α-subunit secreted by the pituitary contains O-linked oligosaccharide, and that secretion of this form of α differs from that of LH dimer.

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