Iodide i g - 



study was the saliva level related to the plasma level or the rate 

 of secretion. Wills (1940, 1943) injected carrier free F 19 into cats 

 and collected submaxillary saliva. The saliva/plasma fluoride ratio 

 was in the range 0-064-0-131 whereas the ratio obtained in the 

 same animals for chloride was 0-315-0-423. No studies were done 

 relating fluoride secretion in saliva either to the total plasma level 

 or to the rate of saliva secretion. Fluoride is therefore secreted in 

 saliva at a lower concentration than the other halides. 



It has been suggested that the low concentration of fluoride in 

 saliva is due to the indiffusibility of fluoride caused by the forma- 

 tion of insoluble calcium fluoride complexes in the blood. This is 

 unlikely since the solubility of CaF 2 in plasma is approximately 

 0-5 mEq/1. (Stuber and Lang, 1929) while the blood concentration 

 is only about o-i mEq/1. , and also because Wills (1940) found that 

 after intravenous injection F 19 distributed itself in 37 per cent of 

 the body weight (as compared to 24 per cent for chloride), i.e. it 

 distributed itself at least as readily as chloride in a predominantly 

 extracellular location. Further studies on fluoride in saliva would 

 be very welcome. 



IODIDE, THIOCYANATE, PERCHLORATE AND NITRATE 



The secretion of iodide in saliva was first noted by Bernard 

 (1856). Lipschitz (1929a, b) showed that iodide was considerably 

 concentrated in dog parotid saliva (and gastric juice) above the 

 plasma level and that the saliva/plasma ratio was reduced when the 

 plasma iodide concentration was raised sufficiently. 



Whilst iodide is secreted in all salivas so far examined the 

 ability to secrete at concentrations higher than the plasma level is 

 not found in all glands. The results of an extensive study by 

 Cohen and Myant (1959) of the secretions in which iodide is con- 

 centrated are shown in Table I. The human parotid gland seems 

 to be the most active of any of those extensively studied. At low 

 rates of secretion, the concentration of iodide is highest and at flow 

 rates above 0-5 ml./min, the s/p ratio becomes constant at about 

 10 and does not change with further increase of saliva secretion 

 rate (Ferguson, Naimark and Hildes, 1956); somewhat similar 

 results have been obtained with the dog parotid (Burgen and 

 Seeman, 1957) although the concentration ratio is lower than in 

 man (Fig. 8.9). 



The secretion of iodide can be expressed as a clearance. Owing 



