Summary. Distribution of the radioactivity of labeled aspartate transaminase from the soluble fraction of pig heart was studied 8 hrs after intravenous injection in piglets in the tissue and the subcellular fractions.The radioactivity was high in the total mass of muscle, followed by that in skin and the intestinal organs. Related to the weight of tissue, the radioactivity is high in kidney, lymph nodes, stomach, liver, and small intestine. It is low in fat, muscle and brain. On separation of the subcellular fractions by differential ccntrifugation it has been found that 60 to 80~o of the PBI radioactivity occurs in the 100 000 g supernatant fraction in liver, renal cortex, and small intestine. Among the non-soluble fractions, the PBI radioactivity was significantly higher only in the mitochondrial fraction of the liver. 91~o of the protein bound radioactivity in the sera can be precipitated with specific antibody at the time of the exsangnination. The preeipitability of protein bound radioactivity with antibody in the i00000 g supernatant fraction of renal cortex, liver, and small intestine amounted to 84, 81 and 91~o resp. almost the same as in the sera.Key words: Enzyme catabolism --Iodine labeling --Piglet.In previous reports we have contended that nonmitochondrial asparrate transaminase from pig heart 1 is not degraded in the intravascular system as is also the case for plasma proteins [11,12]. Its passage through the intestinal wall is negligible, and the intestine does not play an important role in its disappearance from the intravascular pool [13]. The main purpose of the present investigation was to study the distribution of this enzyme in various organs and subcellular compartments, and the immunological behavior of the protein after its disappearance from the vascular system.
Material and Methods
