IODOPROTEINS IN THYROID TISSUE AND BLOOD OF RATS WITH A TRANSPLANTABLE THYROID TUMOR1

Abstract

Lodoprotcins other than thyroglobulin have been detected in a transplantable rat thyroid tumor (Wollman) in which iodine compounds were labeled with I¹³¹ cither in vivo or in vitro. Two types of iodoprotein were found. One was not extractable from glass homogenized tissue by 0.15 M NaCl, and is termed “particulatc iodoprotein, ” or “P-l.” In in vivo experiments, it increased with time after I¹³¹ administration from about 15% to about 70% of the total organic iodine in the tumor. Cell particle fractionation identified this material with the “nuclear” fraction. The second type of iodoprotein was readily extracted from previously frozen (tissue slices. Unlike thyroglobulin, it was soluble in 1.89.M KH₂PO₄ – K₂(HPO.₄ sedimented slowly in the ultracentrifuge, and appeared multidispcrse on zone electrophoresis. This iodoprotein fraction comprised 3 to 9% of the soluble ido-proteins, the remainder being thyroglobulin, and its amount relative to thyro-globulin did not change with time after I¹³¹ administration. It has been termed “thyroid S–l iodoprotein”. Rats bearing the thyroid tumor were also found to have iodoprotein circulating in the blood. Characterization of this material revealed it to be similar to thyroid S–l iodoprotein, but perhaps not identical. It has been termed “serum S–l iodoprotein.”