Gonadotropin stimulation of cyclic adenosine monophosphate and testosterone production without detectable high-affinity binding sites in purified Leydig cells from rat testis
| Autor: | Elizabeth S. Browne, Vinod K. Bhalla |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Male
endocrine system medicine.medical_specialty medicine.drug_class Clinical Biochemistry Cell Separation Testicle Biology Biochemistry Chorionic Gonadotropin Human chorionic gonadotropin Iodine Radioisotopes chemistry.chemical_compound Endocrinology Internal medicine medicine Centrifugation Density Gradient Cyclic AMP Animals Cyclic adenosine monophosphate Testosterone Receptor Molecular Biology reproductive and urinary physiology Pharmacology Leydig cell urogenital system Organic Chemistry Leydig Cells In vitro Rats medicine.anatomical_structure chemistry Gonadotropin hormones hormone substitutes and hormone antagonists |
| Zdroj: | Steroids. 56(2) |
| ISSN: | 0039-128X |
| Popis: | Rat testicular interstitial cells were separated by three different gradient-density procedures and, with each, two biochemically and morphologically distinct cell fractions were isolated. The lighter density cells in fraction-I bound iodine 125-labeled human chorionic gonadotropin (hCG) with high-affinity (apparent equilibrium dissociation constant, K d , approximately 10 −10 m ) without producing either cyclic adenosine monophosphate or testosterone in response to hormone action. The heavier-density cells displayed morphologic features typical of Leydig cells and produced cyclic adenosine monophosphate and testosterone in the presence of hCG without detectable 125 I-labeled hCG high-affinity binding. These cell fractions were further characterized by studies using deglycosylated hCG, a known antagonist to hCG action. Cell concentration-dependent studies with purified Leydig cells revealed that maximal testosterone production was achieved when lower cell concentrations (0.5 × 10 6 cells/250 μl) were used for in vitro hCG stimulation assays. Under these conditions, the 125 I-labeled hCG binding was barely detectable (2.24 fmol; 2,698 sites/cell). Furthermore, these studies revealed that the hCG-specific binding in Leydig cells is overestimated by the classic method for nonspecific binding correction using excess unlabeled hormone. An alternate method is presented. |
| Databáze: | OpenAIRE |
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