Differential processing of the two subunits of human choriogonadotropin (hCG) by granulosa cells. I. Preparation and characterization of selectively labeled hCG

Journal Article · Tue Dec 01 00:00:00 EST 1981 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-109-6-1851· OSTI ID:5403017

Landefeld, T D; Byrne, M D; Campbell, K L; Midgley, Jr, A R

The alpha- and beta-subunits of hCG were radioiodinated and recombined with unlabeled complementary subunits. The resultant recombined hormones, selectively labeled in either the alpha- or beta-subunit, were separated from unrecombined subunit by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, extracted with Triton X-100, and characterized by binding analysis. The estimates of maximum binding (active fraction) of the two resultant selectively labeled, recombined hCG preparations, determined with excess receptor were 0.41 and 0.59. These values are similar to those obtained when hCG is labeled as an intact molecule. The specific activities of the recombined preparations were estimated by four different methods, and the resulting values were used in combination with the active fraction estimates to determine the concentrations of active free and bound hormone. Binding analyses were run using varying concentrations of both labeled and unlabeled hormone. Estimates of the equilibrium dissociation binding constant (Kd) and receptor capacity were calculated in three different ways. The mean estimates of capacity (52.6 and 52.7 fmol/mg tissue) and Kd (66.6 and 65.7 pM) for the two preparations were indistinguishable. Additionally, these values were similar to values reported previously for hCG radioiodinated as an intact molecule. The availability of well characterized, selectively labeled hCG preparations provides new tools for studying the mechanism of action and the target cell processing of the subunits of this hormone.

• Research Organization: Department of Pathology, The University of Michigan, Ann Arbor
• OSTI ID: 5403017
• Journal Information: Endocrinology; (United States), Vol. 109:6
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
HCG
LABELLING
RECEPTORS
CHEMICAL BONDS
CHEMICAL PREPARATION
ELECTROPHORESIS
IODINATION
IODINE 125
IODINE 131
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GONADOTROPINS
HALOGENATION
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOISOTOPES
SYNTHESIS
551001* - Physiological Systems- Tracer Techniques
400702 - Radiochemistry & Nuclear Chemistry- Properties of Radioactive Materials