The effect of 20-hete on vascular tone on resistance and conduit type arteries of trained rats

Objective: It is well known that there are various adaptations which affect vascular tone in arteries after regular physical activities. There hasn't been any study in literature for 20-Hydroxyeicosatetraenoic acid (20-HETE) that has an effect on regulation of local circulation, while it is known that many contractile and relaxant mediators contribute to changes in vascular tone at rest conditions. In this study, we aimed to investigate the effect of 20-HETE, which is known to be vasoconstrictive in many vascular beds, on vascular tone in resistance and conduit type arteries and the probable changes on its contribution to systemic blood pressure as a result of regular physical activities. Method: 6-8 month old Wistar rats were divided into two groups, control and exercise. Exercise group were subjected to swimming exercise for 5 day/week, 1 hour/day for 8 weeks. Intra-arterial mean blood pressure was measured from carotid artery. The direct effect of 20-HETE on vascular tone in the conduit type artery (thoracic aorta) and resistance vessels (gastrocnemius and mesenteric arteries) and its contribution to the effects of various vasoactive substances were evaluated in organ bath and myograf. 20-HETE levels and the expression of CYP4A, the enzyme responsible for 20-HETE production, were measured in isolated vessels. Results: It has been found that the contribution of 20-HETE on regulation of blood pressure is reduced as a result of regular swimming exercises. It has been obviously observed that 20-HETE's contribution to vascular tonus is decreased both directly and caused to decrease response to various vasoconstrictive agents in gastrocnemius resistance vessels, but this effect was not obtained in torasic aort and mesenteric arteries. CYP4A expression and 20-HETE production were decreased in the gastrocnemius vessels. Conclusion: It has been demonstrated that depending on exercise, the effect of 20-HETE on regulation of blood pressure and its vasoconstrictive contribution on vascular tonus in gastrocnemius resistance artery are decreased, and these effects are associated with the decrease of CYP4A protein. Key words: 20-HETE, CYP4A, vascular tone, myograph, exercise