Sodium handling by aging human parotid glands is inconsistent with a two-stage secretion model.

Sodium handling by stimulated human parotid glands was evaluated in male and female subjects across the adult life-span. Young adults secreted more sodium in saliva than their middle-aged and older counterparts. To assess the extent of ductal sodium reabsorption on sodium levels calculated to be present in parotid primary secretory fluid, the relationship between sodium output and parotid saliva flow rate was analyzed. Results are inconsistent with a simple two-stage model of salivary secretion.