Tissue Distribution of Entrapped 1311 - Labeled Injected into Rats

TAKADA, G., ONODERA, II. and TADA, K. Tissue Distribution of Unentrapped or Liposome-Entrapped 1311-Labeled f3-Galactosidase Injected into Rats. Tohoku J. exp. Med., 1981, 134 (2), 103-114 Either unentrapped (free) or liposomeentrapped 131I-labeled 9-galactosidase was injected into rats from tail veins. Tissue distribution and intracellular localization of the radioactivity of both sources were compared. The half-life of liposome-entrapped enzyme in the circulation was much longer than that of the free enzyme. The radioactivity removed from the circulation was recovered primarily in the liver, and to a lesser extent in almost all tissues studied. A small but significant uptake of liposomeentrapped enzyme by the brain was also observed. Uptake of liposome-entrapped enzyme was greater than that of free enzyme in the spleen, heart, lungs and brain, excepting the liver and kidneys. Subcellular fractionation showed distribution of the radioactivity of liposome-entrapped enzyme favoring the mitochondrial-lysosomal fraction from these tissues except the heart. There was a difference in the pattern of intracellular distribution of the radioactivity in the brain of rats between the administration of free enzyme and that of liposomeentrapped enzyme. These findings suggest that when liposomes containing (galactosidase were injected into rats from the tail veins, they would penetrate the blood-brain barrier and would reach the lysosomes in the central nervous system tissue more effectively than the free enzyme itself. j9-galactosidase; liposome; enzyme replacement therapy; rat tissues; 1311