184 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



ranged from 30 to 35°/oo during the period of 

 observation. Starting 24 hours after dosage, skin, 

 muscle, liver, and gonad of sacrificed croaker 

 were radioassayed periodically, and retention 

 curves were drawn by inspection (fig. 5). These 

 curves were then analyzed and replotted by the 

 methods described above. The curve for skin is 

 presented (fig. 6) as a typical example, and reten- 

 tion data on all the tissues are presented in 

 table 4. 



2000 



240 



Figure 5. — Retention of Cs'" by certain croalier tissues 

 following a single oral dose. Curves fitted by inspec- 

 tion. 



The concentration of Cs'" by sldn was rela- 

 tively low at zero time as compared to the other 

 tissues and decreased rapidly for several days. 

 The retention cm've consisted of three rate func- 

 tions or components with ty^s of 6.2, 26.2, and 290.0 

 days (fig. 6). These components represented 87, 

 10, and 3 percent of the amount of Cs'" at zero 

 time. 



Muscle continued to accumulate Cs'" until the 

 14th day, which was considered zero time in 

 calculating retention rates. Althougli the con- 

 centration in muscle was relatively low in the 

 beginning, the slow elimination rate resulted in a 



240 



Figure 6. — Retention of Cs'" by croaker skin, showing 

 separation of a typical composite curve into three rate 

 functions. 



relatively high concentration after 219 days. 

 The composite retention curve was resolved into 

 two rate functions with f^'s of 34.8 and 94.7 days, 

 representing 35 and 61 percent of the amount of 

 Cs''' in muscle at zero time. The sum of both 

 components was only 96 percent leaving a deficit 

 of 4 percent which probably was masked by indi- 

 vidual variation in samples. The retention of 

 Cs'" by rat muscle was expressed as a 2-component 

 curve with ^j^'s of 8 and 16 days, representing 55 

 and 45 percent of the Cs"' at zero time (Ballon 

 and Thompson, 1958). 



Gonads accumulated Cs'" for 7 days before 

 reaching a maximum concentration, which was 

 considerably higher than that of skin and muscle. 

 Although ehmination of Cs'" was fau-ly rapid, 

 the concentration remained higher than that of 

 skin and muscle at the end of the experiment. 



