Aims: 

Based on our experience regarding endothelium-dependent relaxation (EDR) in resistance mesenteric arteries, we started an investigation upon renal interlobar arteries of the rat.

Methods: 

Isometric myography was used to study interlobar renal arteries (1 mm rings, ~200 mm diameter) from adult male Wistar rat. We used a bicarbonate buffer physiological saline solution, at 37°C, bubbled with 95%O₂ + 5% CO₂; pH 7.2 – 7.4. After 2 h equilibration under 1 g tension, in the ring precontracted by 0.01 mM phenylephrine we have separately examined: global EDR induced by 0.01 mM carbachol, the EDHF component of EDR (in presence of 0.01 mM L-NAME and 0.01 mM indomethacin, to inhibit cyclooxygenase and nitric-oxide-synthase), and the participation of calcium-dependent potassium channels (K_Ca) in the EDHF phenomenon, using tetraethylammonium 0.01 mM as inhibitor. The results are expressed as residual active tension, % from the precontraction level (mean ± ESM; n = 4).

Results: 

The EDHF response (42.5 ± 3.3%) is blocked by the K_Ca inhibitor (97.5 ± 5.4%). The results are compared to those obtained by other authors in pig interlobar renal arteries and in upstream renal vascular fragments from Wistar-Kyoto and Sprague-Dawley rats, mice and rabbits.

Conclusion: 

This is the first study regarding the physiological relevance of EDHF in rat interlobar renal arteries and data show that it has a participation comparable with NO, involving K_Ca.

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