Effects of Different Tastants on Parotid Saliva Flow and Composition

Abstract

Saliva from parotid glands plays a role in taste perception. Parotid saliva is also stimulated by tastants. The aim of this work is to investigate the effects of different tastants on the parotid salivary response in six subjects. Five tastants were given in different concentrations in solution and held in the mouth for 10 s. The flow rate, protein concentration, and pH of secreted parotid saliva were monitored continuously for 5 min. Stimulation by tastants on flow rate response consists of an immediate rise in flow followed by a plateau and a rapid return to prestimulus flow. Response of pH results in a slower increase while protein concentration consists in a slower decrease, both followed by a return to prestimulus levels in about 4 min. From a resting flow rate of about 140 μL/min, an increase in flow rate to 370 μL/min was caused by stimulation for 10 s with 10 mL of solutions of 0.01 M citric acid, 0.13 M MgSO4, 0.25 M monosodium glutamate, 0.5 M NaCl, or 0.5 M sucrose. Comparisons of the different tastants showed that the pH of stimulated parotid saliva increased linearly (r = 0.9), irrespective of the nature of the tastant. Protein concentration decreased (r = −0.45) and protein amount increases (r = 0.58) with increase in flow rate for all tastants. Corrected for the effects of flow rate, protein amount depended on the nature of the tastant with the greatest secretion after stimulation by citric acid. Flow rate was largely responsible for pH but tastant appears to play an additional role with flow rate on protein secretion.