Abstract
[3H]‐clonidine binds reversibly to membranes prepared from regions of guinea‐pig kidney. Higher levels of binding were obtained in the membranes prepared from renal cortex (2.15 ± 0.27 pmol/g wet wt.) than renal medulla (0.53 ± 0.07 pmol/g wet wt.) or papilla (0.14 ± 0.06 pmol/g wet wt.; n = 4). Scatchard analysis performed by addition of unlabelled clonidine (1 to 30 pmol) gave figures for the dissociation constant (Kd) for the binding of [3H]‐clonidine to renal cortical membranes of 9.0 ± 0.8 nm and Bmax of 21.6 ± 1.7 pmol/g wet wt. (n = 4). Hill plots of these data gave gradients close to unity, indicating a lack of co‐operative site interactions. The monovalent cations, sodium and potassium, and the divalent cation, calcium, produced concentration‐dependent decreases in [3H]‐clonidine binding to membranes prepared from renal cortex, the EC50s being respectively 25 mm, 37 mm and 23 mm. At low concentrations the divalent cations, magnesium (1 mm) and manganese (0.1 mm), produced enhancement of [3H]‐clonidine binding. At higher concentrations (> 10 mm) both divalent cations inhibited binding. Scatchard analysis of [3H]‐clonidine binding performed in the presence of sodium (100 mm), magnesium (1 mm) or manganese (0.1 mm) revealed that the alterations in binding are primarily due to changes in apparent affinity rather than a change in the number of binding sites. Sodium (100 mm) produced a change in the Kd from 7.0 ± 0.4 nm (n = 8) to 42.3 ± 27.5 nm (n = 3), whereas magnesium (1 mm) decreased the Kd to 6.0 ± 0.9 nm and manganese (0.1 mm) to 4.0 ± 1.0 nm (n = 3). The results indicate that [3H]‐clonidine labels a binding site that has properties resembling an α2‐adrenoceptor, located in the renal cortex. The changes produced by the addition of monovalent and divalent cations are entirely due to changes in the apparent affinity of [3H]‐clonidine binding. 1980 British Pharmacological Society
| Original language | English |
|---|---|
| Pages (from-to) | 57-63 |
| Number of pages | 7 |
| Journal | British Journal of Pharmacology |
| Volume | 71 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Jan 1980 |
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[3H]‐CLONIDINE BINDING TO α‐ADRENOCEPTORS IN MEMBRANES PREPARED FROM REGIONS OF GUINEA‐PIG KIDNEY : ALTERATION BY MONOVALENT AND DIVALENT CATIONS. / SUMMERS, R. J.
In: British Journal of Pharmacology, Vol. 71, No. 1, 01.01.1980, p. 57-63.Research output: Contribution to journal › Article › Research › peer-review
TY - JOUR
T1 - [3H]‐CLONIDINE BINDING TO α‐ADRENOCEPTORS IN MEMBRANES PREPARED FROM REGIONS OF GUINEA‐PIG KIDNEY
T2 - ALTERATION BY MONOVALENT AND DIVALENT CATIONS
AU - SUMMERS, R. J.
PY - 1980/1/1
Y1 - 1980/1/1
N2 - [3H]‐clonidine binds reversibly to membranes prepared from regions of guinea‐pig kidney. Higher levels of binding were obtained in the membranes prepared from renal cortex (2.15 ± 0.27 pmol/g wet wt.) than renal medulla (0.53 ± 0.07 pmol/g wet wt.) or papilla (0.14 ± 0.06 pmol/g wet wt.; n = 4). Scatchard analysis performed by addition of unlabelled clonidine (1 to 30 pmol) gave figures for the dissociation constant (Kd) for the binding of [3H]‐clonidine to renal cortical membranes of 9.0 ± 0.8 nm and Bmax of 21.6 ± 1.7 pmol/g wet wt. (n = 4). Hill plots of these data gave gradients close to unity, indicating a lack of co‐operative site interactions. The monovalent cations, sodium and potassium, and the divalent cation, calcium, produced concentration‐dependent decreases in [3H]‐clonidine binding to membranes prepared from renal cortex, the EC50s being respectively 25 mm, 37 mm and 23 mm. At low concentrations the divalent cations, magnesium (1 mm) and manganese (0.1 mm), produced enhancement of [3H]‐clonidine binding. At higher concentrations (> 10 mm) both divalent cations inhibited binding. Scatchard analysis of [3H]‐clonidine binding performed in the presence of sodium (100 mm), magnesium (1 mm) or manganese (0.1 mm) revealed that the alterations in binding are primarily due to changes in apparent affinity rather than a change in the number of binding sites. Sodium (100 mm) produced a change in the Kd from 7.0 ± 0.4 nm (n = 8) to 42.3 ± 27.5 nm (n = 3), whereas magnesium (1 mm) decreased the Kd to 6.0 ± 0.9 nm and manganese (0.1 mm) to 4.0 ± 1.0 nm (n = 3). The results indicate that [3H]‐clonidine labels a binding site that has properties resembling an α2‐adrenoceptor, located in the renal cortex. The changes produced by the addition of monovalent and divalent cations are entirely due to changes in the apparent affinity of [3H]‐clonidine binding. 1980 British Pharmacological Society
AB - [3H]‐clonidine binds reversibly to membranes prepared from regions of guinea‐pig kidney. Higher levels of binding were obtained in the membranes prepared from renal cortex (2.15 ± 0.27 pmol/g wet wt.) than renal medulla (0.53 ± 0.07 pmol/g wet wt.) or papilla (0.14 ± 0.06 pmol/g wet wt.; n = 4). Scatchard analysis performed by addition of unlabelled clonidine (1 to 30 pmol) gave figures for the dissociation constant (Kd) for the binding of [3H]‐clonidine to renal cortical membranes of 9.0 ± 0.8 nm and Bmax of 21.6 ± 1.7 pmol/g wet wt. (n = 4). Hill plots of these data gave gradients close to unity, indicating a lack of co‐operative site interactions. The monovalent cations, sodium and potassium, and the divalent cation, calcium, produced concentration‐dependent decreases in [3H]‐clonidine binding to membranes prepared from renal cortex, the EC50s being respectively 25 mm, 37 mm and 23 mm. At low concentrations the divalent cations, magnesium (1 mm) and manganese (0.1 mm), produced enhancement of [3H]‐clonidine binding. At higher concentrations (> 10 mm) both divalent cations inhibited binding. Scatchard analysis of [3H]‐clonidine binding performed in the presence of sodium (100 mm), magnesium (1 mm) or manganese (0.1 mm) revealed that the alterations in binding are primarily due to changes in apparent affinity rather than a change in the number of binding sites. Sodium (100 mm) produced a change in the Kd from 7.0 ± 0.4 nm (n = 8) to 42.3 ± 27.5 nm (n = 3), whereas magnesium (1 mm) decreased the Kd to 6.0 ± 0.9 nm and manganese (0.1 mm) to 4.0 ± 1.0 nm (n = 3). The results indicate that [3H]‐clonidine labels a binding site that has properties resembling an α2‐adrenoceptor, located in the renal cortex. The changes produced by the addition of monovalent and divalent cations are entirely due to changes in the apparent affinity of [3H]‐clonidine binding. 1980 British Pharmacological Society
UR - http://www.scopus.com/inward/record.url?scp=0019225336&partnerID=8YFLogxK
U2 - 10.1111/j.1476-5381.1980.tb10909.x
DO - 10.1111/j.1476-5381.1980.tb10909.x
M3 - Article
VL - 71
SP - 57
EP - 63
JO - British Journal of Pharmacology
JF - British Journal of Pharmacology
SN - 1476-5381
IS - 1
ER -