Participation of nitric oxide in regional coronary bloodflow regulation during myocardial ischemia in the canine heart (part 12).

11 Sep
2012

The changes in flow in the present experiments represent changes at the time of ischemia occurrence by a partial occlusion of a coronary artery, while those during reactive hyperemia correspond to changes at the time of repayment of flow after ischemia produced by the total occlusion of a coronary artery. Therefore, transmural flow distribution during reactive hyperemia does not necessarily represent the sole effect of ischemia, but also the effect of reperfusion. If during reactive hyperemia a large part of the nitric oxide produced is due to the sudden increase in shear stress at the time of reopening the vessel, then more nitric oxide may be produced in subepicardial vessels due to a greater shear stress in the vessels of this region than in deeper vessels, as suggested by the longer time constant for reflow of the subendocardial vessels .This view is supported by the sequential changes of transmural flow distribution (as measured by serial injections of microspheres) during reactive hyperemia from a preferential subepicardial flow to a uniform distribution, and finally to a preferential subendocardial flow . On the other hand, this transmural difference of shear stress should not be expected in a steady state ischemia as in the present experiments, and if the signal for nitric oxide production is a direct function of the degree of ischemia, as it is for hypoxia , then nitric oxide should be released in a greater proportion in the subendocardial layer because this region is more vulnerable to coronary flow reduction due to its higher oxygen consumption. You have a great opportunity to discover the pharmacy that will always be sure to live up to your highest expectations, no matter if you would like to get Claritin online tablets or buy any other prescription medicine with no prescription required on very advantageous terms.

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