The glycocalyx constitutes the first line of the blood tissue interface and is thus involved in many physiological processes, deregulation of which may lead to microvascular dysfunction. Because administration of LPS is accompanied by severe microvascular dysfunction, the purpose of the study was to investigate microvascular glycocalyx function during endotoxemia. Bolus infusion of LPS (10 mg kg(-1)) to male Sprague-Dawley rats elicited the development of hyporeactivity to vasoactive agents and microvascular derangements, including decreased capillary density and significant increases in intermittent and stopped flow capillaries in the small intestine muscularis layer compared with controls. LPS elicited plasma hyluronan release and reduction in endothelial surface thickness, indicative of glycocalyx degradation. Because endothelial glycocalyx is extremely sensitive to free radicals, oxidative stress was evaluated by oxidation of dihydrorhodamine in microvascular beds and levels of heart malondialdehyde and plasma carbonyl proteins, which were all increased in LPS-treated rats. Activated protein C (240 microg kg(-1) h(-1)) enhanced systemic arterial pressure response to norepinephrine in LPS-treated rats. Activated protein C (240 microg kg(-1) h(-1)) prevented capillary perfusion deficit in the septic microvasculature that were associated with reduced oxidative stress and preservation of glycocalyx. Our findings support the conclusion that LPS induces major microcirculation dysfunction accompanied by microvascular oxidative stress and glycocalyx degradation that may be limited by activated protein C treatment.

Background-Although most of the deleterious effects of sepsis-induced apoptosis have been attributed to increased lymphocyte cell death, caspase activation may directly alter cell function of different organ systems. We postulated that left ventricular (LV) cardiomyocyte caspase activation is directly involved in sepsis-induced heart contractile dysfunction. Methods and Results-LV cardiomyocytes isolated 4 hours after rat treatment with endotoxin injection (10 mg/kg) displayed major reductions in contractile reserve and myofilament response to Ca 2ϩ . Concomitantly, endotoxin also induced increases in LV cardiomyocyte caspase-3, -8, and -9-like activities, which were associated with sarcomeric structure destruction and cleavage of components of the cardiac myofilament. Interestingly, zVAD.fmk treatment of septic rat prevented LV cardiomyocyte contractile dysfunction, reductions in myofilament response to calcium, troponin T cleavage, and sarcomere destruction. Serum (10%) of endotoxin-treated rats induced contractile dysfunction, caspase-3-like activity increase, and troponin T cleavage of naive LV cardiomyocytes. The effects of septic serum were prevented in LV cardiomyocytes isolated from zVAD.fmk-or zDEVD.cmk-treated rats or LV cardiomyocytes preincubated with zVAD.fmk or zDEVD.cmk. Conclusions-The

Introduction Frequency-dependent acceleration of relaxation (FDAR) ensures appropriate ventricular filling at high heart rates and results from accelerated sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) activity independent of calcium removal from the cell. Because lipopolysaccharide (LPS) challenge may induce aberrations in calcium trafficking and protein phosphorylation, we tested whether LPS would abolish FDAR in rats.

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