Abstract
An increased myocardial β-adrenergic receptor density has been reported following myocardial ischemia. However, it is not clear whether these receptors are effectively coupled to adenylate cyclase which would be necessary for enhanced physiological responsiveness. We, therefore, examined the effects of myocardial ischemia in six conscious dogs (4 intact and 2 with posterior wall denervation) in which the left circumflex coronary artery was occluded. Ischemia was verified by measurement of regional blood flow by radioactive microspheres. After 1 h of coronary artery occlusion, the dogs were anesthetized with pentobarbital and the left ventricle was divided into normal, intermediate and ischemic regions. A crude membrane fraction was prepared from each region. β-Adrenergic receptors were quantitated with 125I-cyanopidolol binding and adenylate cyclase activity was measured. In all, six animals studied, β-adrenergic receptor density increased progressively and adenylate cyclase activity decreased progressively, when the ischemic myocardium was compared to the intermediate and the non-ischemic myocardium. Since adenylate cyclase activity declined, these results do not support the concept that the increased β-receptor density induced by myocardial ischemia is causally related to enhanced β-adrenergic sensitivity.
Original language | English (US) |
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Pages (from-to) | 75-82 |
Number of pages | 8 |
Journal | Journal of Molecular and Cellular Cardiology |
Volume | 20 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1988 |
Funding
Six adult mongrel dogs of either sex were anesthetized with sodium pentobarbital Supported in part by USPHS grants # HL26215, HL33065, HL28189, HL38070 and RR00168. 0022-2828/88/010075 + 08 $03.00/0 9 1988 Academic Press Limited
Keywords
- Adenylate cyclase
- Coronary artery occlusion
- Ischemia
- Micropheres
- β-Adrenergic receptors
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Molecular Biology