Nature of Iodine in Fish
After separation of the supernatant and precipitate of the homogenized fish, the entire
iodine content, both radioactive and stable,was found to be present in the supernatant,the washed precipitate being free from iodine. On further study of the supernatant fraction,it was found that (1) after precipitation of proteins by TCA, the entire radioactivity remained in the supernatant fraction, none was present in the washed precipitate ; (2) after TCA precipitation, resin chromatography of the supernatant on Dowex 1 resin showed that no radioactive or stable iodine was eluted at pH 1 .4, the pH at which thyroid hormone ıvould have appeared in the eluate ; and (3) the extraction of radioactive and stable iodine from the supernatant by acid butanol was PH) per cent. After washing with alkali, no radioactivity or stable iodine remained in the butanol phase.
After dialysis of fish homogenate, no iodine could be detected in the homogenate indicating that all the iodine present was diffusible.
The total iodine concentration of the pooled haddock serum was 1,480 gig. per 100 ml. After passage through the Amberlite resin no iodine was detected in the eluate, indicating that virtually all the serum iodine was present in inorganic form.
These results indicate that all the iodine present in the fillet, both radioactive and stable,was present in inorganic form, and no thyroxme-like compounds or iodoproteins were detected either before or after cooking.