Fundamental evaluation for hepatic accumulation of 99mTc-galactosyl human serum albumin

99mTc-galactosyl human serum albumin (GSA) is a radioactive agent for diagnosing liver diseases. Accumulation of the agent to the liver decreases as the liver function deteriorates. Also hepatic blood flow is suspected to play a role in its accumulation to the liver. These contributing factors were examined by using a rat model with hepatic cellular damage or decreased hepatic blood flow. When hepatic blood flow was decreased by ligating the portal vein or superior mesenteric vein, the uptake ratio of GSA to the liver decreased when the agent was injected into the tail vein. However, the first pass extraction ratio of GSA by the liver did not decrease when the agent was injected directly into the portal vein. When hepatic cellular damage was induced by peritoneal administration of D-galactosamine, both uptake ratio and first pass extraction ratio of GSA were decreased in proportion to the dose of D-galactosamine administered. However, neither uptake ratio nor first pass extraction ratio of radioactive colloid did change at all in the damaged liver. In conclusion, hepatic blood flow plays an important role in liver uptake of GSA and the accumulation of GSA to the liver reflects the degree of hepatic cellular damage. (author)