Benzodiazepine receptors along the nephron: [3H]PK 11195 binding in rat tubules |
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Authors: | D Butlen |
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Affiliation: | Laboratoire de Physiologie Cellulaire, Collège de France, 11, place Marcelin Berthelot, 75231 Paris Cédex 05, France |
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Abstract: | Binding of [3H]PK 11195, an isoquinoline carboxamide derivative, was measured in microdissected tubule segments of rat nephron. High specific binding capacities (1.1-1.8 fmol X mm-1) were found in the thick ascending limb of the Henle's loop and in the collecting tubule, whereas specific binding could not be detected in the proximal tubule. In the medullary collecting tubule, the association and dissociation rate constants at 4 degrees C were k1 = 3.0 X 10(6) M-1 X min-1 and k-1 = 0.021 min -1; the ratio k-1/k1 = 7.0 nM was in agreement with the estimated equilibrium dissociation constant (Kd = 2.4 nM). [3H]PK 11195 binding sites from medullary ascending limb and medullary collecting tubule revealed the following sequence of specificity: PK 11195 = Ro 5-4864 much greater than clonazepam, indicating that tubule binding sites might be the peripheral benzodiazepine receptors of the rat kidney. |
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Keywords: | Nephron microdissection PK 11195 binding Benzodiazepine PCT, proximal convoluted tubule PR, pars recta MAL, medullary thick ascending limb CAL, cortical ascending limb CCT, cortical collecting tubule MCT, medullary collecting tubule |
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