CIRCULATION PROFILE OF TC-99M LABELED LIPOSOME-ENCAPSULATED HEMOGLOBIN IN A 10-PERCENT OR 50-PERCENT RAT HYPOVOLEMIC SHOCK MODEL

The circulation kinetics and organ biodistribution of liposome encapsu lated hemoglobin (LEH) was determined non-invasively in hypovolemic ra ts using a technetium-99m (Tc-99m) liposome labeling procedure. Rats w ith an indwelling catheter had either 10% or 50% of their blood volume removed and replaced with an equal volume of LEH labeled with Tc-99m (Tc-99m LEH). Mean arterial pressures and heart rates were monitored t hroughout the experiment. Gamma camera images were acquired during the first 90 minutes following infusion of the Tc-99m LEH and at 20 hours post-infusion. Blood capillaries were drawn at various times to monit or Tc-99m activity and the amount of LEH remaining in circulation. The re were significant differences in the kinetics and biodistribution fo r the two groups. In the 10% group, the LEH was removed quickly from c irculation with only 0.9% remaining at 20 hours, while the 50% group h ad 51.2% at 20 hours. The liver and spleen were the major organs respo nsible for LEH clearance. The 20 hour biodistribution by tissue sampli ng showed that the 10% group had 37.6% in the liver and 34.3% in the s pleen, while the 50% group had only 18.4% in the liver and 14.6% in th e spleen.