Visualization of high- and low-affinity beta-adrenergic receptors in rat lung: upregulation by chronic hypoxia.

Abstract

Chronic hypoxia induces a hyperadrenergic state which down-regulates beta-adrenergic receptors (beta-AR) in the heart. We visualized lung beta-AR binding sites after adaptation to chronic hypoxia by autoradiography of whole lung sections labeled with 50 pM 125I-labeled pindolol. A low concentration of agonist (32 nM isoproterenol) selectively masked beta-ARs with high affinity for agonists. Total specific beta-AR binding increased twofold with hypoxia. In both the control and hypoxic lung sections, 60-70% of the beta-ARs were in a high-affinity state, which could be reversed by guanine nucleotide. Autoradiography revealed a high density of high- and low-affinity beta-AR sites in lung parenchyma, predominantly involving alveolar walls, but also the walls of airways and blood vessels. The distribution of high- and low-affinity beta-AR within the lung was qualitatively identical. Hypoxia increased beta-AR binding without affecting its distribution. The majority of the additional beta-ARs induced during adaptation to chronic hypoxia are in the high-affinity state, and are thus of probable functional significance.

• Authors: D J Birnkrant, P B Davis, P Ernsberger
• Journal: The American journal of physiology (Am J Physiol) Vol. 265 Issue 4 Pt 1 Pg. L389-94 (Oct 1993) ISSN: 0002-9513 [Print] United States
• PMID: 8238373 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Receptors, Adrenergic, beta
• Guanylyl Imidodiphosphate
• Sodium
• Pindolol
• Isoproterenol

Topics

• Animals
• Autoradiography
• Chronic Disease
• Guanylyl Imidodiphosphate (pharmacology)
• Hypoxia (metabolism)
• Isoproterenol (pharmacology)
• Lung (metabolism)
• Male
• Pindolol (antagonists & inhibitors, metabolism)
• Rats
• Rats, Wistar
• Receptors, Adrenergic, beta (metabolism)
• Reference Values
• Sodium (pharmacology)
• Up-Regulation