ABSTRACT
The effect of liposome-encapsulated hemoglobin (LEH) was tested in a rodent model of limb ischemia and reperfusion--causing local reperfusion injury and a cascade of systemic responses. Intracellular pH (pHi) and phosphocreatine (PCr)/inorganic phosphate (Pi) ratio were serially monitored using ³¹P-nuclear magnetic resonance spectroscopy with a 2-cm solenoid coil on a rodent hind limb. After baseline measurements, the right hind limb underwent ischemia for 70 min, followed 10 min later by intravenous administration of LEH (10 mL/kg, n = 6), homologous red blood cells (RBCs, n = 6), saline (n = 6), or no treatment (n = 6). Reperfusion was then observed for an additional 60 min. While pHi decreased precipitously after the onset of ischemia and even following reperfusion, LEH-treated rats had significantly milder intracellular acidosis compared with all other groups during ischemia, and after reperfusion as well throughout the observation with the saline-treated rats. In contrast, the PCr/Pi ratio decreased regardless of treatment after ischemia until reperfusion, when the ratio returned toward normal or the energy status improved only in the LEH-treated rats, while the ratio remained depressed in the control animals receiving RBC, saline, or no treatment. Morphological studies 7 days later revealed a tendency toward suppressed mononuclear cell infiltration with preservation of muscular mass and structure in the LEH-treated rats. LEH treatment after early limb ischemia appeared to improve intracellular energy metabolism and eventually preserve skeletal muscle in a rodent model of limb ischemia and reperfusion.