The inhibitory effect of the perchlorate ion on the concentration of iodide and pertechnetate has been studied in human parotid saliva, collected under resting conditions and during stimulation. The saliva/plasma (S/P) 132 I and 99m TcO 4 ‐ ratios and the salivary I and TcO 4 ‐ clearances fell after perchlorate administration. The percentage fall in the S/P ratios was greatest under resting conditions. The effect of increasing doses of perchlorate on the S/P I and TcO 4 ‐ ratios was studied. There was a linear inverse relation between the S/P ratios and log. dose of perchlorate at perchlorate doses of 3 mM/day and greater. I ‐ and TcO 4 ‐ are not inhibited to the same extent by perchlorate. The ratio of the salivary I ‐ to TcO 4 ‐ clearance, measured simultaneously, was higher after perchlorate administration. The dose of perchlorate corresponding to inhibition of the S/P TcO 4 ‐ ratio to half the control value was less than the dose required for a corresponding decrease in the S/P I ‐ ratio. The dose of perchlorate required to depress the S/P I ‐ and TcO 4 ‐ ratios to 50 per cent of the control value and to an absolute value of 0·5 was compared to the dose of iodide required to produce similar falls. It was concluded that perchlorate is a more potent inhibitor of the salivary iodide concentrating mechanism than iodide given in molal equivalent doses. Iodide, however, in contrast to perchlorate, depressed the S/P I ‐ and TcO 4 ‐ ratios to the same extent. Although TcO 4 ‐ shares with I ‐ one common transport mechanism, there are also differences in the transport of the ions from the blood into the saliva.
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Harden et al. (1968) studied this question.