The importance of EDHF in endothelium-dependent relaxation increases distally in mesenteric arteries depending upon the contracting agent.

AIM

The importance of endothelium-derived hyperpolarizing factor (EDHF) in endothelium-dependent relaxation (EDR) is influenced by multiple factors, including vascular territory and caliber, pre-existing tone and its determining factors.

METHOD

Using isometric myography we noticed that in rat mesenteric resistance arteries (RMA2; 2nd order branches) EDHF-mediated relaxation is increased when precontraction is induced by prostaglandin F2 (PGF) compared to phenylephrine (PHE) and we investigated the participation of certain K channels. Here we extend the study on more proximal vascular fragments; from mesenteric arcade and from 1st order branches.

RESULTS

The EDHF component of EDR is stronger distally only when precontraction is induced by PHE. Moreover, morphometric analysis shows a strong inverse correlation between the magnitude of EDHF response and arterial caliber.

CONCLUSIONS

Other authors have shown that EDHF increases in relative importance distally, but we show that this change in EDR profile depends upon the contracting agent used, with implications regarding the physiological relevance of accumulated data refering to EDHF and nitric oxide as mediators of EDR in resistance arteries.