The long-term goal of our research is to investigate physiological bases of changes that occur in cells in animal models which simulate septic states seen after trauma and surgery. In this study, we will evaluate cell membrane function in the skeletal muscle in rat bacteremic and endotoxic shock model. Our recent studies have shown increased intracellular exchangeable calcium and a state of cellular calcium dyshomeostasis in skeletal muscle in the endotoxic rat. We hypothesize that alleviation of the shock-related calcium dyshomeostasis could restore cellular functions and thus provide protection against shock lethality. The main thrust of the proposed experiments will be to test this hypothesis with respect to shock induced alterations in cellular calcium homeostasis and sugar and amino acid transport and their insulin regulation in the skeletal muscle. We will invetigate the effects of Ca2+ antagonists, Diltiazem, Verapamil and Nifedipine which could potentially prevent and/or attenuate the influx of extracellular Ca2+ into cell. Ca2+ antagonists will be administrated to rats before or after intravenous injection of endotoxin (endotoxic shock) or Gram-negative bacteria (bacteremic shock). Sugar and amino acid transport will be studied by measuring transport of nonmetabolizeable substrates, 3-0 methyl glucose (3MG( and alpha-amino isobutyric acid (AIB) by control or experimental rat soleus muscles, in vitro, in the absence and presence of insulin. Intracellular exchangeable calcium will be measured by initially """"""""loading"""""""" intact rat soleus muscle with 45Ca and then by desaturating 45Ca from muscles to resolve the 45Ca exchanging cellular compartment and its size. To evaluate the relationship between altered Ca2+ homeostasis and 3MG and AIB transport, control rat soleus muscles will be initially exposed to the Ca2+ ionophore, A23187. The 3MG and AIB transport by A23187 exposed muscle will then be determined. To ascertain the effects of Ca2+ antagonists via their actions at the vascular smooth and cardiac muscle cells, in vivo effects of the antagonists will be compared with their in vitro effectgs on 3MG and AIB transport. These studies will elucidate the role of cellular Ca2+ dyshomeostasis in altered sugar and minio acid transport and insulin regulation in skeletal muscle during shock and will provide insights into therapeutic effects of Ca2+ antagonists in shock.
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