Jan 1, 1994

Long-term exposure to norepinephrine results in down-regulation and reduced mRNA expression of pulmonary beta-adrenergic receptors in guinea pigs

American Journal of Respiratory Cell and Molecular Biology
M NishikawaP J Barnes

Abstract

We studied the down-regulation of beta 2-adrenoceptors in guinea pig lung after chronic exposure to a beta-agonist. Guinea pigs were exposed to either norepinephrine (NE) or vehicle for 7 days. The density and affinity of beta-adrenoceptors were determined by Scatchard analysis of [125I]cyanopindolol binding in a lung membrane preparation and beta 1- and beta 2-adrenoceptor subtypes were studied in the presence of 0.1 microM ICI 118,551, a selective beta 2-adrenoceptor antagonist, or 0.1 microM CGP 20712 A, a selective beta 1-adrenoceptor antagonist, respectively. beta 2-Adrenoceptor mRNA was examined by Northern blot analysis. The tissue distribution of beta 2-adrenoceptors and of beta 2-adrenoceptor mRNA in lung after NE infusion were determined using receptor autoradiography and in situ hybridization, respectively. The functional significance of the decrease in beta 2-adrenoceptor was tested by measuring the relaxation response to a beta 2-agonist in isolated parenchymal strips. NE treatment resulted in decreases of 75 +/- 9%, 84 +/- 4%, and 66 +/- 9% of total beta-, beta 1-, and beta 2-adrenoceptors in the lung, compared with control animals. The administration of NE had only minimal effects on the dissociation constant (Kd...Continue Reading

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Mentioned in this Paper

Establishment and Maintenance of Localization
Northern Blotting
ICI 118551
Lung
Cavia
Alveolar
Antagonist Muscle Action
Receptor Down-Regulation
Norepinephrine, (+, -)-Isomer
CGP 20712

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