title: Testicular FSH receptor numbers and affinity in bulls of various ages.
abstract: 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--18h at 25 degrees 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 x 10(9) 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.
mesh_terms: D000375:Aging; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D008297:Male; D009929:Organ Size; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011962:Receptors, FSH; D013737:Testis / Q000033:anatomy & histology / Q000378:metabolism*
chemical_list: D011956:Receptors, Cell Surface; D011962:Receptors, FSH; D005640:Follicle Stimulating Hormone