This study was undertaken to investigate the role of nitric oxide (NO), cyclooxygenase products and bradykinin (Bk) receptors in the Bk evoked responses of canine renal arteries and perfused kidneys. Rings of isolated canine renal arteries were mounted in organ chambers for measurement of isometric force. The isolated canine kidneys were perfused with Krebs-solution (constant flow) and the perfusion pressure was continuously recorded. The influence of the cyclooxygenase inhibitor indomethacin and the nitric oxide (NO) synthase inhibitor Nw-nitro-L-arginin (L-NOARG) on the vasocontractile responses to phenylephrine (PE) were examined in both preparations. Furthermore, the effects of Bk on the tone of canine isolated renal arteries and on the vasopressor responses of isolated buffer-perfused kidneys of dogs were tested in the absence and presence of enzyme inhibitors and the B2 kinin receptor antagonist HOE-140. It was found that indomethacin enhanced the contractile responses of large renal arteries to PE by 77±10%. In intact artery rings L-NOARG (0.1 mM) caused an additional potentiation of the PE-induced contractions in the presence of indomethacin (from 11.5±1.2 mN to 21.6±1.7 mN). However, L-NOARG failed to affect contractile responses to PE in endothelium-denuded rings. Bk produced a concentration-dependent relaxation of the precontracted endothelium-intact renal arteries. The IC50 value for Bk was 11.2±3.7 nM. The relaxant activity of the peptide in renal artery rings was not affected by indomethacin (3 μM). However, in the presence of L-NOARG a significantly higher concentration (IC50=860±300 nM) of Bk was required to relax renal arteries. The Bk receptor antagonist HOE-140 (10 nM for 40 min) attenuated the relaxant effect of Bk in renal artery rings (from an IC50 of 14.2±2.5 nM to 216±37 nM).
|Number of pages||10|
|Journal||Acta physiologica Hungarica|
|Publication status||Published - Dec 1 1996|
ASJC Scopus subject areas
- Physiology (medical)