Contribution of carbon monoxide on vascular tonus in different vascular beds and segments. A descriptive study

Contribution of Carbon Monoxide on Vascular Tonus in Different Vascular Beds and Segments. A Descriptive StudyCO is considered as an important mediator released from endothelium and smooth muscles and is responsible for regulating vascular tonus. Although CO has been known that is produced in many vascular tissues endogenously with enzymes HO-1 and HO-2, it has not been shown that contribution of CO to which vessel bed or in which ratio. The purpose of this descriptive study is to determine the contribution of CO to vascular tonus in vascular segments of various sizes and in vascular bed of various organs and through which mechanisms CO causes vasodilatation in these vessels. For this purpose, we used 6-8 months old Wistar Albino rats weighing 300-350 g. The arteries were carefully dissected out and were mounted on a myograph or tissue bath. Endogenous and exogenous vessel responses were studied in vascular beds of mesentery (main mesenteric artery, 1st, 2nd, 3rd branches), renal (renal artery, 1st, 2nd, 3rd branches), gastrocinemius muscle (feed artery, 1st, 2nd branches), gracilis muscle (femoral artery, muscular brunch, gracilis artery) heart (coroner, LAD), lung (main pulmonary artery, pulmonary artery, 1st branch), brain (pial artery), vascular beds, thoracic and abdominal aorta. To determine whether endogenously produced CO contributes to vascular tonus, PE or Ser concentration-response curves were generated in all vessels before and after treatment with the HO inhibitor CrMP. To examine vasodilator responses to CO donor (CORM, Tricarbonyldichlororuthenium (II) dimer) were elicited in each ring on three separate occasions following pre-constriction with Phe or Ser: first in the absence of inhibitors, second in the presence of cGMP inhibitor 1H-[1,2,4]Oxadiazolo[4,3-a] quinox-alin-1-one (ODQ) and third in the presence of non specific potassium channel inhibitor tetraethylammonium (TEA). Moreover, HO-2 expression from isolated vessels was found using the western blot analysis. While CO has contributed to vascular tonus regulation of thoracic and abdominal aorta, mesentery, renal, pulmonary, heart, gastrocinemius feed artery, it has not affected in resistance arteries of these vascular beds. Carbon monoxide was not effective at all vascular bed of gracilis muscle but it was also significantly effective in the regulation of vascular tone in resistance arteries of the brain tissue. It has been shown that, the contribution of HO-2 enzyme protein levels and the endogenous carbon monoxide to vascular tone is not related to each other. While CO generally shows the relaxant effect in smooth muscle via potassium channels in arterial vessels which are lesser than 600 ?m, it performs the relaxant effect via either potassium channels or cGMP in the larger arteries.