cesium"' in marine fishes 



181 



Figure 3. — Concentration of Cs"' in tissues of croaker following a single oral dose. 



amount of Cs'" in the organs did not diminish. 

 In the present experiment, the supply of Cs'" was 

 Uinited by a single dose in the digestive tract. 

 Consequently, instead of maximum levels of 

 activity being maintained in the tissues, peaks of 

 concentration were reached at certain time inter- 

 vals following ingestion. 



T.\BLE 1. — Cs'^^ remaining in digestive tracts of croaker at 

 intervals following oral administration 



All tissues tested concentrated Cs"' to higher 

 levels than blood, which maintained a relatively 

 low and slowly decreasing concentration of the 

 radionuclide. This decrease of radioacti\4ty in 

 the blood probably was an indication of excretion 

 by all tissues tested, since blood serves as a trans- 

 porting medium for them. The early accuimda- 

 tion by liver, kidney, heart, and spleen, along 



with the rapid loss from the digestive tract, indi- 

 cates that the internal organs concentrated most of 

 the radionuclide as soon as it became available in 

 the blood. The accumulation of Cs''" by the gills 

 was high diu-ing the first few hours, but leveled off 

 and began to decrease 24 hours after dosage. 

 Muscle, after an initial brief period of rapid up- 

 take, accumulated the radionuchde at a slower 

 but uniform rate whUe the available Cs'" became 

 reduced in the digestive tract and the other 

 tissues. 



Accumulation and tissue distribution of Cs'" in 

 Uttle tuna from a single oral dose were followed 

 during an 8-day period. As in the croaker, the 

 internal organs took up the radionuclide at a fast 

 rate, concentrating it over levels in the blood; 

 muscle and gonad had slower rates and moderate 

 levels of concentration, while the other tissues had 

 relatively low concentrations (table 2). It is 

 interesting that on the first day 99 percent of the 

 Cs''' in the blood was located in the serum, while 

 on the sixth day only 44 percent was in the serum 

 and 56 percent in the cells. 



The tissue distribution of Cs'" in bluefish was 

 determined 24 hours after oral administration. 

 Tlie results of this test were generally similar to 

 those found for croaker and little tuna (table 3). 



