ISSN:
1432-1912
Keywords:
Coronary Artery
;
Noradrenaline
;
Depolarization
;
Adrenoceptors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Isolated helical strips from coronary arteries of pigs or cattle were activated by potassium-rich solutions. The ED50 for potassium was calculated by means of an exponential function of the dose-response curve. After blockade of the alpha-adrenoceptors by 1.4 μg/ml of phenoxybenzamine the ED50 was not changed (37.4 and 37.2 mval K, respectively), but decreased to 29.4 mval K after blockade of the beta-adrenoceptors by 6.3 μg/ml of propranolol. — The maximum dilating concentration of noradrenaline for the polarized preparation was about 1 μg/ml. Noradrenaline relaxed the depolarized, contracted preparation in potassium-rich solution (135 mval K), too. Therefore, it seems that changes of the membrane potential are not required for the coronary dilatation elicited by stimulation of betaadrenoceptors. After blockade of the alpha-adrenoceptor the dilatory effect of noradrenaline was enhanced, whereas after blockade of the beta-adrenoceptors noradrenaline induced a contraction. Concerning physiological concentrations at the vascular smooth muscle of coronary arteries both adrenotropic receptors were activated by noradrenaline. The changes of contractile tension observed were discussed with respect to variations of intracellular calcium ion concentration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00501127
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