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Physiological variation in alpha-adrenoceptor-mediated arterial sensitivity: relation to agonist affinity.
Science (New York, N.Y.)
|October 10, 1986
Summary
Vascular smooth muscle sensitivity to norepinephrine varies by artery. Agonist affinity, not receptor reserve, primarily determines this sensitivity, suggesting local regulation of norepinephrine responses in arteries.
Area of Science:
- Pharmacology
- Physiology
- Cardiovascular Research
Background:
- Vascular smooth muscle (VSM) exhibits varying responses to vasoactive agents across different arterial beds.
- Norepinephrine (NE) is a key mediator of vascular tone, but factors influencing its efficacy in different arteries are not fully understood.
Purpose of the Study:
- To investigate the determinants of differential sensitivity to norepinephrine in rabbit arterial smooth muscle.
- To elucidate the roles of alpha-adrenoceptor affinity and receptor reserve in mediating NE sensitivity.
Main Methods:
- Comparative analysis of norepinephrine sensitivity in VSM from various rabbit arteries.
- Assessment of alpha-adrenoceptor agonist dissociation constant and receptor reserve.
Main Results:
- VSM sensitivity to norepinephrine varied significantly among different rabbit arteries, even after controlling for known factors.
- Norepinephrine sensitivity showed a linear correlation with the agonist dissociation constant (Kd) of the alpha-adrenoceptor.
- Receptor reserve was not found to be a significant determinant of norepinephrine sensitivity.
Conclusions:
- Agonist affinity for the alpha-adrenoceptor is the primary factor determining norepinephrine sensitivity in these rabbit arteries.
- This affinity-driven sensitivity appears to be a locally regulated characteristic of VSM.
- Local regulation of agonist affinity may explain regional variations in vascular responses to norepinephrine.