Comparative characterization of β-adrenoceptors in the bladder, heart, and lungs of rats: Alterations in spontaneously hypertensive rats.

The present study aimed to characterize and compare β-adrenoceptors in the rat bladder with those in the heart and lungs of SD rats (8-10 weeks old) using subtype-selective agonists and antagonists in a radioligand binding assay with (-)-[I]cyanopindolol ([I]CYP), and also to clarify alterations in β-adrenoceptors in the bladder of spontaneously hypertensive rats (SHR) at 14 weeks old, from those of Wistar-Kyoto rats (WKY) and Wistar rats at the same age. A radioligand binding assay with [I]CYP was used to measure β-adrenoceptor binding activity in rat tissues. Metoprolol exhibited the highest affinity to specific binding sites of [I]CYP in the rat heart, indicating the dominance of β-adrenoceptors.

Comparative characterization of lung muscarinic receptor binding after intratracheal administration of tiotropium, ipratropium, and glycopyrrolate.

The aim of the current study was to characterize comparatively the binding of muscarinic receptor in the lung of rats intratracheally administered anticholinergic agents (tiotropium, ipratropium, glycopyrrolate) used clinically to treat chronic obstructive pulmonary disease (COPD) and asthma. Binding parameters of [N-methyl-(3)H]scopolamine methyl chloride ([(3)H]NMS) were determined in tissues (lung, bladder, submaxillary gland) of rats intratracheally administered tiotropium, ipratropium, and glycopyrrolate. The in vitro binding affinity of tiotropium for the receptors was 10-11-fold higher than those of ipratropium and glycopyrrolate.