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Species differences in regulation of alpha-adrenergic receptor function
Y T Shen1, D E Vatner, H E Gagnon
1Department of Medicine, Harvard Medical School, Massachusetts General Hospital, Boston.
The American Journal of Physiology
|November 1, 1989
Summary
Rats exhibit significantly higher alpha-1 adrenergic receptor density and responsiveness compared to other mammals. This explains their unique physiological response to alpha-adrenergic agonists like phenylephrine.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
- Comparative Medicine
Background:
- Alpha-adrenergic receptors play a crucial role in regulating cardiovascular function.
- Species-specific differences in autonomic receptor expression can lead to varied physiological responses.
Purpose of the Study:
- To compare the effects of alpha-adrenergic stimulation on cardiovascular parameters across different mammalian species.
- To investigate the correlation between alpha-adrenergic receptor density and physiological responsiveness.
Main Methods:
- Conscious baboons, calves, dogs, and rats were studied.
- Left ventricular pressure and its maximum rate of development (dP/dt) were measured after beta-adrenergic and muscarinic blockade.
- Autonomic receptor density was quantified in cardiac sarcolemmal preparations.
Main Results:
- Rats showed the most significant increase in LV dP/dt upon phenylephrine administration (29% increase).
- This heightened response in rats correlated with the highest alpha-1 adrenergic receptor density (73 fmol/mg).
- Other species like dogs, calves, and baboons exhibited progressively lower responses and receptor densities.
Conclusions:
- Significant interspecies variations exist in alpha-adrenergic receptor density and function among mammals.
- Alpha-1 adrenergic receptor density is a key determinant of the physiological response to alpha-adrenergic agonists.