Gargling-induced reduction in urinary Na/K ratio in dehydrated humans: Is there a dual role for oropharnygeal receptors in vasopressin regulation?

Abstract

Background: A linear relationship exists between plasma osmolality (Posm) and thirst perception (TP) and also between plasma arginine vasopressin (Pavp) and Posm. Thus, an increase in Posm leads to an increase in Pavp secretion, which are systemic indicators of thirst. Recent studies have also shown that Pavp secretion is associated with sodium retention. The role of Pavp in termination of thirst during drinking while Posm remains unchanged is however inconclusive. This informed the basis for the present study. Methods: Ten (10) apparently healthy male volunteers aged between 20 and 30 years, non-smokers and not on any medication prior to the experiments, were recruited for this study. They dehydrated for 18hrs and their 12-hour urine samples as well as thirst perception were measured with standard methods and compared with those of 10 euhydrate control subjects. Urine volume as well sodium and potassium concentrations were estimated. Results: We observed a gradual decrease in TP of the subject who gargled with D/H₂o; this decrease became significant (P<0.05, respectively) after 30mins and remained so till the end of the experiment. Gargling with various concentrations of saline (0.9 - 2.7%) did not show any significant change; however, in comparison with controls, the Na⁺/K⁺ ratio significantly decreased in all samples collected after gargling at every 30mins for 1Hr and after ad libitum distilled water drinking (P<0.05, respectively). Also, the Na/K ratio obtained during gargling (30mins and 60mins) were relatively stable but decreased significantly (P<0.05) at 90mins; which was 30mins after ad libitum drinking. Conclusion: We conclude that oropharygeal receptors play a dual role in stimulating immediate inhibition of vasopressin as well as aldosterone release in the regulation of thirst during dehydration and gargling, to eliminate thirst.