NITRIC-OXIDE SYNTHASE INHIBITION NEGATES SEPTIC-INDUCED ALTERATIONS IN CYTOPLASMIC CALCIUM HOMEOSTASIS AND MEMBRANE DYNAMICS

This study was undertaken to evaluate the role of nitric oxide (NO) in the sepsis-induced disruption of intracellular calcium homeostasis an d membrane dynamics. Anticoagulated whole blood was obtained from 10 h ealthy volunteers. Equal aliquots were incubated with saline (control) , 2 mu g/mL Escherichia coli endotoxin (lipopolysaccharide), 8 mu g/mL NO inhibitor, N-monomethyl arginine (NMA), and endotoxin plus NO inhi bitor (lipopolysaccharide/NMA). Erythrocytes were harvested, washed, a nd loaded with the calcium chelator, FURA-2AM, and the fluorescent mem brane probe TMA-DPH. Cells were evaluated for both intracellular calci um concentration and membrane viscosity (anisotropy) by fluorescent sp ectrophotometry. Endotoxin induced a significant increase in both intr acellular calcium concentration and anisotropy. NMA had no intrinsic a ffect on either of these cellular characteristics. NMA was, however, e ffective in preventing the endotoxin-induced changes. These results su ggest that NO may play a role in the disruption of intracellular calci um homeostasis and erythrocyte membrane deformability noted in sepsis.