Testicular FSH receptor numbers and affinity in bulls of various ages

in Reproduction
Authors:
J. A. Dias
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J. J. Reeves
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DOI:
https://doi.org/10.1530/jrf.0.0660039
Volume/Issue:
Volume 66: Issue 1
Page Range:
39–45
Article Type:
Research Article
Online Publication Date:
Sep 1982
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Summary. Bulls (N = 42) ranging in age from 1 day to 5.5 years were used to determine whether a change in the concentration of FSH receptors in the bovine testis occurred as bulls matured. 125I-labelled human FSH was used as the ligand to evaluate binding to bovine testicular membranes. Membrane fractions were collected by centrifugation of testicular homogenates at 120 g and recentrifugation of the 120 g supernatant at 1250 g. Relative binding activity of membrane sedimented at 1250 g was determined after incubation of membranes with 125I-labelled FSH for 16–18 h at 25°C, followed by centrifugation (1250 g) to separate bound from free hormone. Specifically bound FSH when expressed as fmol/mg protein was negatively correlated with age (r = —0·73). The association constant (Ka) determined by Scatchard analysis was the same for bulls at all ages with a mean (± s.e.m.) Ka = 1·5 ± 0·3 × 109 m−1. Concentration of FSH receptors on a per mg protein basis declined rapidly from birth to 2.5 years of age and remained low up to 5.5 years of age. On a whole testis basis the total number of receptors increased as the bulls matured. After 2.5 years of age total testicular binding did not change.

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Print ISSN:
1470-1626
Online ISSN:
1741-7899