Background-During ischemia, the intracellular calcium and inorganic phosphate (P i ) concentrations rise and pH falls. We investigated the effects of these changes on force development in donor and failing human hearts to determine if altered contractile protein composition during heart failure changes the myocardial response to Ca 2ϩ , P i , and pH. Methods and Results-Isometric force was studied in mechanically isolated Triton-skinned single myocytes from left ventricular myocardium. Force declined with added P i to 0.33Ϯ0.02 of the control force (pH 7.1, 0 mmol/L P i ) at 30 mmol/L P i and increased with pH from 0.64Ϯ0.03 at pH 6.2 to 1.27Ϯ0.02 at pH 7.4. Force dependency on P i and pH did not differ between donor and failing hearts. Incubation of myocytes in a P i -containing activating solution caused a potentiation of force, which was larger at submaximal than at maximal [Ca 2ϩ ]. Ca 2ϩ sensitivity of force was similar in donor hearts and hearts with moderate cardiac disease, but in end-stage failing myocardium it was significantly increased. The degree of myosin light chain 2 phosphorylation was significantly decreased in end-stage failing compared with donor myocardium, resulting in an inverse correlation between Ca 2ϩ responsiveness of force and myosin light chain 2 phosphorylation. Conclusions-Our results indicate that contractile protein alterations in human end-stage heart failure alter Ca

Objective-Advanced glycation end products (AGEs), such as N -(carboxymethyl)lysine (CML), are implicated in vascular disease. We previously reported increased CML accumulation in small intramyocardial blood vessels in diabetes patients. Diabetes patients have an increased risk for acute myocardial infarction (AMI). Here, we examined a putative relationship between CML and AMI. Methods and Results-Heart tissue was stained for CML, myeloperoxidase, and E-selectin in AMI patients (nϭ26), myocarditis patients (nϭ17), and control patients (nϭ15). In AMI patients, CML depositions were 3-fold increased compared with controls in the small intramyocardial blood vessels and predominantly colocalized with activated endothelium (E-selectin-positive) both in infarction and noninfarction areas. A trend of increased CML positivity of the intima of epicardial coronary arteries did not reach significance in AMI patients. In the rat heart AMI model, CML depositions were undetectable after 24 hours of reperfusion, but became clearly visible after 5 days of reperfusion. In line with an inflammatory contribution, human myocarditis was also accompanied by accumulation of CML on the endothelium of intramyocardial blood vessels. Conclusions-CML, present predominantly on activated endothelium in small intramyocardial blood vessels in patients with AMI, might reflect an increased risk for AMI rather than being a result of AMI.

In coronary artery bypass surgery , the patency of arterial grafts is higher than that of venous grafts because of vein-graft disease , which involves excessive proliferation of venous smooth muscle cells (SMCs) and subsequent accelerated atherosclerosis. We studied the function of TR3 nuclear orphan receptor (TR3) in the early response of SMCs to mechanical strain , a major initiator of vein-graft disease. We demonstrate that TR3 expression is induced in human saphenous vein segments exposed ex vivo to whole-blood perfusion under arterial pressure. Cultured venous SMCs challenged by cyclic stretch displayed TR3 induction and enhanced DNA synthesis , whereas SMCs derived from the internal mammary artery remained quiescent. Small-interfering RNA-mediated knockdown of TR3 and adenovirus-mediated overexpression of TR3 in venous SMCs enhanced and abolished stretch-induced DNA synthesis , respectively. Accordingly, in organ cultures of wild-type murine vessel segments exposed to cyclic stretch, p27Kip1 was down-regulated, whereas expression of this cell cycle inhibitor was unaffected by cyclic stretch in TR3-transgenic vessels, concordant with a lower proliferative response. Finally, stretch-mediated proliferation was inhibited by 6-mercaptopurine, an agonist of TR3. In conclusion, TR3 represents inhibitory mechanisms to restrict venous SMC proliferation and may contribute to prevention of veingraft disease.

These measurements indicate that it is possible to study the correlation between mechanical properties and protein composition in small biopsies from human ventricular muscle.