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Coexistence of γ‐Aminobutyric Acid Type A and Type B Receptors in Testicular Interstitial Cells
Author(s) -
Ritta Mónica N.,
Campos María B.,
Calandra Ricardo S.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb11416.x
Subject(s) - gabaergic , gabaa receptor , agonist , receptor , population , aminobutyric acid , radioligand , muscimol , medicine , gamma aminobutyric acid , endocrinology , gaba receptor , chemistry , biology , biochemistry , demography , sociology
Abstract: The existence of specific γ‐aminobutyric acid (GABA)ergic receptors in testicular interstitial cells was investigated in the present study. Specific binding of [ 3 H]GABA to interstitial cell membranes was found to be time‐ and temperature‐dependent and varied according to Ca 2+ concentration present in the incubation medium. We analyzed the ability of different GABAergic agonists and antagonists to displace the bound radioactivity. In the absence of Ca 2+ (1 m M EDTA), GABA and the GABAergic agonist isoguvacine displaced the bound radioactivity. When the radioligand assay was performed in the presence of 2.5 m M CaCl 2 , the [ 3 H]GABA specifically bound increased twofold. Under such conditions, the specific GABAergic agonist baclofen, as well as GABA and isoguvacine, displaced the [ 3 H]GABA bound. Saturation analysis revealed the presence of a population of GABA A binding sites with a K D value of 45.2 n M and a maximal number of binding sites of 57.4 fmol/mg of protein. The maximal binding increased on addition of 2.5 m M CaCl 2 to 102 fmol/mg of protein, indicating the existence of a second population of GABAergic receptors, i.e., type B, with essentially the same affinity. In addition, the incubation of testicular interstitial cells with GABA and baclofen resulted in an increase in androgen production. These results support a functional role of GABA in the neuroendocrine control of the male gonad.