Key result
In isolated human radial artery rings, angiotensin II was the most potent vasoconstrictor, and the presence of intact endothelium significantly increased both sensitivity and maximal contraction to angiotensin II and phenylephrine.
Why the study?
Does the presence of functional endothelium alter the contractile properties of isolated human radial arteries exposed to vasoconstrictors or electrical field stimulation?
Does the presence of functional endothelium alter the contractile properties of isolated human radial arteries exposed to vasoconstrictors or electrical field stimulation?
The human radial artery exhibits marked sensitivity to angiotensin II and phenylephrine, which is paradoxically enhanced by the presence of endothelium, suggesting a potential mechanism for perioperative graft spasm.
Should not yet change graft harvesting practice; hypothesis-generating for endothelial modulation to reduce radial artery spasm.
Radial artery (RA) is increasingly used as graft for coronary artery bypass grafting due to its good long-term patency. However, the mechanism of peri- and post-operative spasm is still unclear. Because of that, the aim of our study is to analyze the contractility of RA and to determine whether the presence of functional endothelium alters its contractile properties. Contractions of isolated RA rings were provoked by exogenously applied vasoconstrictors or by electrical field stimulation (EFS, 20 Hz). The order of vasoconstrictors potency based on their EC50 values was as follows: angiotensin II > phenylephrine > 5-hydroxytriptamine. Presence of endothelium increased both EC50 and maximal contraction to phenylephrine and angiotensin II, but inhibited reactivity of RA to 5-hydroxytriptamine. Spontaneous rhythmic contractions (SRC, <4 mHz) and EFS-induced contractions of RA are endothelium-independent and weaker than contractions induced by exogenously applied vasoconstrictors. Our study concludes that RA shows marked sensitivity and reactivity to angiotensin II, phenylephrine, and 5-hydroxytriptamine. Further investigations are necessary to answer why angiotensin II and phenylepehrine induce stronger contractions in the presence of endothelium. In addition, SRC as well as contractions of neurogenic origin may take part in developing vascular spasm of RA.
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Stojnić et al. (2006) studied Coronary artery disease (n=34). Vasoconstrictors (Angiotensin II, Phenylephrine, 5-Hydroxytriptamine) vs. Rings without endothelium was evaluated on Sensitivity (EC50) and reactivity (Emax) to vasoconstrictors. In isolated human radial artery rings, angiotensin II was the most potent vasoconstrictor, and the presence of intact endothelium significantly increased both sensitivity and maximal contraction to angiotensin II and phenylephrine.
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