Summary
The binding of 3H-clonidine to membrane particles from guinea-pig ileum was investigated. The specific binding, i.e. the binding that could be inhibited by high concentrations of unlabeled clonidine or noradrenaline, was of high affinity, K D3 nM. The number of sites was approximately 25 fmol/mg protein. Rate constants of association and dissociation were 5.3×107 M−1 min−1 and 0.18 min−1, respectively. Affinites of various drugs to the binding site were determined by measuring their effect on the binding of 3H-clonidine. The affinity of adrenergic agonists decreased in the order clonidine = tramazoline > (−)-erythro-α-methylnoradrenaline > (−)-noradrenaline ≫ (−)-phenylephrine. (−)-Noradrenaline had about 20 times more affinity than the (+)-isomer. The affinity of α-adrenoceptor antagonists decreased in the order phentolamine > rauwolscine = yohimbine > WB 4101 > pseudoyohimbine > prazosin = corynanthine. Yohimbine and rauwolscine had about 100 times more affinity than their stereoisomer corynanthine. Serotonin 10 μM and metiamide 10 μM did not affect the binding, and propranolol inhibited it only at high concentrations. — The results indicate that 3H-clonidine labels an β2-adrenoceptor in guinea-pig ileum. The orders of affinity of α-adrenoceptor agonists and antagonists agree well with their orders of potency in functional tests, namely as modulators of cholinergic transmission in the guinea-pig ileum and as modulators of noradrenaline release in the rabbit pulmonary artery. An α-adrenoceptor should be classified as α2 when the affinities of clonidine, tramazoline and α-methylnoradrenaline greatly exceed the affinity of phenylephrine, and when the affinities of rauwolscine and yohimbine exceed those of prazosin and corynanthine.
Similar content being viewed by others
References
Berthelsen, S., Pettinger, W. A.: A functional basis for classification of α-adrenergic receptors. Life Sci. 21, 595–606 (1977)
Borowski, E., Starke, K., Ehrl, H., Endo, T.: A comparison of pre-and postsynaptic effects of α-adrenolytic drugs in the pulmonary artery of the rabbit. Neuroscience 2, 285–296 (1977)
Brown, D. A., Caulfield, M. P.: Hyperpolarizing ‘α2’ in rat sympathetic ganglia. Br. J. Pharmacol. 65, 435–445 (1979)
Butler, M., Jenkinson, D. H.: Blockade by WB 4101 of α-adrenoceptors in the rat vas deferens and guinea-pig taenia caeci. Eur. J. Pharmacol. 52, 303–311 (1978)
Cedarbaum, J. M., Aghajanian, G. K.: Catecholamine receptors on locus coeruleus neurons: pharmacological characterization. Eur. J. Pharmacol. 44, 375–385 (1977)
Doxey, J. C., Smith, C. F. C., Walker, J. M.: Selectivity of blocking agents for pre- and postsynaptic α-adrenoceptors. Br. J. Pharmacol. 60, 91–96 (1977)
Drew, G. M.: Pharmacological characterization of the presynaptic α-adrenoceptors regulating cholinergic activity in the guinea-pig ileum. Br. J. Pharmacol. 64, 293–300 (1978)
Dubocovich, M. L., Langer, S. Z.: Negative feed-back regulation of noradrenaline release by nerve stimulation in the perfused cat's spleen: differences in potency of phenoxybenzamine in blocking the pre- and post-synaptic adrenergic receptors. J. Physiol. (Lond.) 237, 505–519 (1974)
Hornung, R., Presek, P., Glossmann, H.: Alpha adrenoceptors in rat brain: direct identification with prazosin. Naunyn-Schmiedeberg's Arch. Pharmacol. 308, 223–230 (1979)
Jarrot, B., Louis, W. J., Summers, R. J.: The characteristics of 3H-clonidine binding to an α-adrenoceptor in membranes from guinea-pig kidney. Br. J. Pharmacol. 65, 663–670 (1979)
Keller, R., Oke, A., Mefford, I., Adams, R. N.: Liquid chromatographic analysis of catecholamines. Routine assay for regional brain mapping. Life Sci. 19, 995–1004 (1976)
Langer, S. Z.: The regulation of transmitter release elicited by nerve stimulation through a presynaptic feed-back mechanism. In: Frontiers in Catecholamine Research (E. Usdin, S. H. Snyder, eds.), pp. 543–549. New York: Pergamon Press 1973
Langer, S. Z.: Presynaptic regulation of catecholamine release. Biochem. Pharmacol. 23, 1793–1800 (1974)
Lasch, P., Jakobs, K. H.: Agonistic and antagonistic effects of various α-adrenergic agonists in human platelets. Naunyn-Schmiedeberg's Arch. Pharmacol. 306, 119–125 (1979)
Lowry, O. H., Rosebrough, N. J., Farr, A. L., Randall, R. J.: Protein measurement with the Folin phenol reagent. J. Biol. Chem. 193, 265–275 (1951)
Medgett, I. C., McCulloch, M. W., Rand, M. J.: Partial agonist action of clonidine on prejunctional and postjunctional α-adrenoceptors. Naunyn-Schmiedeberg's Arch. Pharmacol. 304, 215–221 (1978)
Miach, P. J., Dausse, J. P., Meyer, P.: Direct biochemical demonstration of two types of α-adrenoreceptor in rat brain. Nature 274, 492–494 (1978)
Scatchard, G.: The attraction of proteins for small molecules and ions. Ann. N.Y. Acad. Sci. 51, 660–672 (1949)
Starke, K.: Alpha sympathomimetic inhibition of adrenergic and cholinergic transmission in the rabbit heart. Naunyn-Schmiedeberg's Arch. Pharmacol. 274, 18–45 (1972)
Starke, K., Langer, S. Z.: A note on terminology for presynaptic receptors. In: Presynaptic Receptors (S. Z. Langer, K. Starke, M. L. Dubocovich, eds.), pp. 1–3. Oxford: Pergamon Press 1979
Starke, K., Montel, H., Gayk, W., Merker, R.: Comparison of the effects of clonidine on pre- and postsynaptic adrenoceptors in the rabbit pulmonary artery. Naunyn-Schmiedeberg's Arch. Pharmacol. 285, 133–150 (1974)
Starke, K., Borowski, E., Endo, T.: Preferential blockade of pre-synaptic α-adrenoceptors by yohimbine. Eur. J. Pharmacol. 34, 385–388 (1975a)
Starke, K., Endo, T., Taube, H. D.: Relative pre- and postsynaptic potencies of α-adrenoceptor agonists in the rabbit pulmonary artery. Naunyn-Schmiedeberg's Arch. Pharmacol. 291, 55–78 (1975b)
Tanaka, T., Weitzell, R., Starke, K.: High selectivity of rauwolscine for presynaptic α-adrenoceptors. Eur. J. Pharmacol. 52, 239–240 (1978)
U'Prichard, D. C., Snyder, S. H.: Distinct α-noradrenergic receptors differentiated by binding and physiological relationships. Life Sci. 24, 79–88 (1979)
U'Prichard, D. C., Greenberg, D. A., Snyder, S. H.: Binding characteristics of a radiolabeled agonist and antagonist at central nervous system alpha noradrenergic receptors. Mol. Pharmacol. 13, 454–473 (1977)
U'Prichard, D. C., Chairness, M. E., Robertson, D., Snyder, S. H.: Prazosin: differential affinities for two populations of α-noradrenergic receptor binding sites. Eur. J. Pharmacol. 50, 87–89 (1978)
Weitzell, R., Tanaka, T., Starke, K.: Pre- and postsynaptic effects of yohimbine stereoisomers on noradrenergic transmission in the pulmonary artery of the rabbit. Naunyn-Schmiedeberg's Arch. Pharmacol. 308, 127–136 (1979)
Wikberg, J. E. S.: Pharmacological classification of adrenergic α receptors in the guinea pig. Nature 273, 164–166 (1978a)
Wikberg, J. E. S.: Differentiation between pre- and postjunctional α-receptors in guinea pig ileum and rabbit aorta. Acta Physiol. Scand. 103, 225–239 (1978b)
Williams, L. T., Lefkowitz, R. J.: Receptor binding studies in adrenergic pharmacology. New York: Raven Press 1978
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Tanaka, T., Starke, K. Binding of 3H-clonidine to an α-adrenoceptor in membranes of guinea-pig ileum. Naunyn-Schmiedeberg's Arch. Pharmacol. 309, 207–215 (1979). https://doi.org/10.1007/BF00504752
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00504752