Recovery In Vivo and In Vitro of α-Adrenoceptor Responses and Radioligand Binding After Phenoxybenzamine
| Autor: | Carlene A. Hamilton, John L. Reid, Harris W. Dalrymple |
|---|---|
| Rok vydání: | 1982 |
| Předmět: |
Male
Time Factors Phenoxybenzamine Alpha (ethology) Blood Pressure In Vitro Techniques Pharmacology Ligands Norepinephrine In vivo medicine Animals Binding site Phenylephrine Chemistry Antagonist Heart Receptors Adrenergic alpha In vitro Receptors Adrenergic Dissociation constant Rabbits Cardiology and Cardiovascular Medicine Spleen Muscle Contraction medicine.drug |
| Zdroj: | Journal of Cardiovascular Pharmacology. 4:S125-S128 |
| ISSN: | 0160-2446 |
| DOI: | 10.1097/00005344-198200041-00025 |
| Popis: | Phenoxybenzamine is an irreversible, selective alpha 1-adrenoceptor antagonist that results in long-lasting attenuation of the effects of alpha-adrenoceptor agonists in vivo and in vitro. We have studied in rabbits the time course of recovery of in vivo pressor responses to phenylephrine and in vitro contractile responses of spiral strips of renal artery to phenylephrine and noradrenaline. The maximum number of binding sites and the dissociation constant has been determined using 3H-prazosin in spleen and heart membranes prepared at intervals up to 8 days after phenoxybenzamine 5 mg/kg intravenously. In vitro contractile responses recovered over 2-3 days and by 4 days the EC50 was lower than control. In vivo pressor responses recovered over 5-8 days to control levels. The number of binding sites was only 50% of control at 8 days. It is proposed that under the conditions studied the recovery of binding sites may provide an index of turnover of alpha-adrenoceptors. The results also suggest that postreceptor mechanisms contribute to the increased responses observed in vitro. |
| Databáze: | OpenAIRE |
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