Iodoproteins 



181 



plastin-like activity in saliva, presumably this can be equated with 

 the platelet factor of the later workers. 



IODOPROTEINS 



In the dog, radioactive iodine is incorporated into some of the 

 proteins secreted by the parotid gland (Burgen, Weiss and Weiss, 

 1959). Frequently over 50 per cent of the total iodine secreted is 

 so bound and cannot be extracted by butanol or other organic 

 solvents. After tryptic digestion of the proteins and chromato- 



4«r 



r 



■5 6 

 so 



-to 



24 



■+0 



£ 



20 40 60 



ml. saliva secreted 



80 



Fig. 9.4. Protein concentration in successive 5 -ml. portions of saliva secreted 



by the dog submaxillary gland. 



Data of Anrep (1921). 



graphy most of the iodine is found as monoiodotyrosine and small 

 amounts as di-iodotyrosine but no detectable amounts of thyro- 

 nines. Presumably the iodotyrosines are present in the peptide 

 structure of the proteins. The organic incorporation of iodine is 

 inhibited by thiouracil and other drugs which can block incor- 

 poration of iodine in the thyroid gland. This iodine-containing 

 protein represents only a small proportion of the total salivary 

 protein as judged by paper electrophoresis since the peak of radio- 

 activity is found to lie between the three main peaks of protein 

 concentration present in dog parotid saliva. 



No organic iodine is present in human saliva (Ferguson, Krahn 

 and Hildes, 1958) but organic iodine compounds perhaps similar 



