Specific Binding of β-Adrenergic Catecholamines to a Subcellular Fraction from Cardiac Muscle
Population
78,000 x g subcellular fraction of canine cardiac tissue
Design
Preclinical
Authors
Discussion
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Member takes
Implication
Supports beta-adrenergic binding and adenylate cyclase in canine fractions; hypothesis-generating for human receptor-targeted therapies.
Key Points
- Characterize the specific binding properties of beta-adrenergic catecholamines and associated adenylate cyclase activity in canine cardiac muscle subcellular fractions.
- Isolated a 78,000 x g subcellular fraction from canine cardiac muscle tissue.
- Assayed [3H]norepinephrine binding affinity, stereospecific competition, adenylate cyclase stimulation, and sensitivity to pH, temperature, ions, and enzymatic digestion.
- Evaluated differences from neural vesicle binding using reserpine sensitivity, ATP dependence, and chemical sympathectomy models.
- Norepinephrine concentrated 1,000-fold at 10⁻⁹ M, exhibiting two distinct binding constants (K = 1.04 × 10⁷ M⁻¹ and 1.33 × 10⁶ M⁻¹) alongside two dissociation rates.
- Beta-adrenergic drugs competed for binding in direct proportion to their physiological inotropic potency and stimulated co-localized adenylate cyclase with matching specificity.
- Binding peaked at pH 7.5 and was inhibited by divalent cations (1–5 mM), sulfhydryl reagents, urea, and proteases, but remained unaffected by reserpine or chemical sympathectomy.
Structured PICO
P
Population
78,000 x g subcellular fraction of canine cardiac tissue
I
Intervention
β-Adrenergic catecholamines (including [3H]Norepinephrine)
O
Outcome
Specific binding characteristics of norepinephrinesurrogate
Identifies specific beta-adrenergic catecholamine binding sites in canine cardiac subcellular fractions, distinct from neural vesicles.
Cite This Study
Lefkowitz et al. (1973) studied this question.