Aims: 

Endothelium-dependent relaxation (EDR) differs upon species, age, sex, hormonal status, vascular territory and caliber, vasodilating agent, pre-existing tone. There are few studies regarding the effect of tone, so we investigated the effect of resting tension upon the EDHF response.

Methods: 

We used isometric myography and mesenteric resistance arteries (2 mm rings; ~0.15 mm diameter) from male Wistar rats (200-250 g). After 2 h equilibration under a tension of 1 g or 2 g, the ring was precontracted by 0.01 mM phenylephrine and we tested EDR induced by 0.01 mM carbachol or the EDHF component of EDR (in presence of 0.01 mM L-NAME and 0.01 mM indomethacin). Results are expressed as residual active tension (RAT), % of precontraction level (mean ± SEM; n = 4).

Results: 

The chosen preparation does not display a myogenic response to stretch and carbachol does not decrease baseline tension. Contraction is ~25% stronger in rings pretensioned at 2 g, EDR is complete for both pretension levels, while the EDHF component is more ample (p < 0.01; Student's t-test) at 2 g (45.4 ± 3.1% RAT), vs. 1 g (62.7 ± 2.8% RAT).

Conclusion: 

The antagonism between myogenic response and the EDHF phenomenon is well known, but our novel observations indicate that the release/action of EDHF is potentiated by a simple increase of parietal tension, which may be of functional relevance in both acute and chronic increases of arterial pressure.

*CNCSIS grant A/1222 **CNCSIS grant interdisciplinary platform /68