Objective: 

It is known that aging is associated with increasing in cardiovascular disorders and, endothelial dysfunction has a pivotal role in this process. Endothelial dysfunction observed in aged subject seems to be related with decreased NO production and bioavailability. On the other hand carbon monoxide (CO) is another mediator derived from endothelial cells and it also contributes the regulation of vascular tonus. However, the possible role of CO to endothelial dysfunction in aged rats is not investigated. The aim of this study was to investigate how CO affects the vascular tonus in aged animals.

Methods: 

Young (4 months, n=10) and aged (24 months, n=10) Wistar rats were used in this study. Mesenteric arteries and its first (1A), second (2A) and third (3A) branches were dissected and mounted wire myograph. The contraction responses of vessel segments to phenylephrine (Phe) were determined in the presence and absence of heme oxygenase inhibitor (CRMP) and all protocols were achieved in the presence of L-NAME.

Results: 

The contraction response to Phe in the presence of CRMP was significantly increased in main mesenteric arteries obtained from both of young and aged animals (p<0.001). Maximal response values to Phe in the presence of CRMP were significant decreased in old compared to young animals (p<0.001). CRMP did not alter vasoconstriction responses to Phe of other mesenterial arterial segments.

Conclusions: 

These results demonstrated that endogen CO is involved in the regulation of vascular tonus in conduit type in mesenteric bed, but not in small arteries, and, this involvement is attenuated in aged rats.