Altered reactivity of tertiary mesenteric arteries following acute myocardial ischemia.

Background: It is unknown if cardiac ischemia has any deleterious effect on the contractile properties of nonischemic, peripheral vascular beds. Thus, the objective of the present study was to determine whether acute myocardial ischemia results in peripheral vascular dysfunction.

Methods And Results: This study characterized force maintenance and the sensitivity to acetylcholine (ACh)-mediated smooth muscle (SM) relaxation of tertiary (3rd) mesenteric arteries from Sprague-Dawley rats following 30 min of myocardial ischemia. Both the phosphorylation of nonmuscle (NM) light chain (LC) and SM-LCs as well as the expression of myosin phosphatase targeting subunit 1 (MYPT1) were also determined. Our data demonstrate that acute myocardial ischemia resulted in vascular dysfunction of 3rd mesenteric vessels, characterized by decreases in force maintenance, ACh- and cGMP-mediated SM relaxation, the phosphorylation of NM-LCs and SM-LCs, and MYPT1 expression. Ischemia was also associated with an increase in protein polyubiquitination, suggesting that during ischemia MYPT1 is targeted for degradation or proteolysis.

Conclusion: Acute myocardial ischemia produces peripheral vascular dysfunction; the changes in LC phosphorylation and MYPT1 expression result in a decrease in both tone and the sensitivity to NO-mediated SM relaxation of the peripheral vasculature.