Aim: 

Radial artery has increased its popularity as an alternative arterial conduit in coronary artery bypass grafting surgery. Nevertheless, little is known about the functional behaviour of the radial artery in healthy subjects, avoiding confounding cardiovascular risk factors. The aim of this study was to analyze the noradrenaline-elicited contractions of radial artery segments from pig, a well-established animal experimental model.

Methods: 

Immunohistochemistry was conducted to localize dopamine-beta-hydroxylase protein expression in the radial artery wall. Arterial rings were suspended in organ baths for isometric recording of tension. Frequency-response and exogenous noradrenaline concentration-responses curves were performed in preparations under resting conditions.

Results: 

Morphological studies revealed adrenergic nerve fibers innervating the radial artery wall. Electrical field stimulation-induced responses were practically abolished by tetrodotoxin, guanethidine and prazosin, thus indicating the adrenergic nature of the neurogenic contractions. Concentration-dependent contractions to noradrenaline were primarily inhibited by prazosin and to a lesser extent by rauwolscine but were not modified by propranolol. Endothelium removal, nitric oxide synthase, soluble guanylate cyclase and cyclooxygenase inhibition, potassium channel blockade, oxygen reactive species removal and endothelin receptor blockade did not alter exogenous noradrenaline response.

Conclusion: 

The porcine radial artery wall presents adrenergic nerves fibers. Adrenergic stimulation produced a contractile response mainly mediated through a₁-adrenoceptor activation. However, no endothelial mechanisms were shown to be involved in the modulation of the exogenous noradrenaline-elicited responses. These findings provide a better understanding of the adrenergic receptor-dependent contractile response in healthy subjects.

This work was supported by a grant from FIS [PI031257]