Salt Taste

Our ability to detect salt (NaCl) in food and beverages (salt taste) depends on the activity of taste cells, biological sensors localized in the oral cavity. Salt taste is mainly due to sodium ions and has a huge impact on our lifestyle by guiding food preferences. The use of animal models has allowed us to decipher the mechanisms used by taste cells to recognize Na+. It is now known that at least two parallel signaling routes exist in most mammals, including humans. One is called the amiloride-sensitive (AS) pathway because it relies on a specific molecular receptor to detect Na+, the epithelial sodium channel (ENaC), which is highly sensitive to the blocking effect of amiloride, a diuretic drug. This pathway is extremely selective in detecting Na+ over other cations. The other one is called amiloride-insensitive (AI) pathway because is not affected by amiloride. This mechanism is not selective for Na+, and can detect a variety of cations. The molecular receptor(s) for this pathway, however, is (are) still unknown. In rodents, AS pathway is crucial for recognizing Na+ and underlies preference responses to low-moderate concentrations of NaCl in water. On the contrary, the AI pathway is preferentially recruited when NaCl concentrations are high and it mediates rejection responses. Psychophysical studies indicate that salt taste is a very complex sensory activity in humans, which hardly can be reduced to only two separate signaling pathways. Besides the actual concentration of Na+ in the saliva, which represents the stimulus for taste cells, other factors may contribute substantially to modify what we actually perceived as salty. The positive hedonic tone of salt taste may lead to sodium overconsumption, a risk factor for the development of hypertension. Understanding salt taste mechanisms represents the prerequisite to improve food products and therefore our health.