Aging and secretory reserve capacity of major salivary glands.

A loss of acinar cells occurs with aging, while salivary production remains age-stable in healthy adults. It is hypothesized that a secretory reserve exists to preserve function despite a loss of acinar cells in normal aging. The purpose of this double-blind, placebo-controlled, crossover study was to determine age-related differences in salivary response to an anti-sialogogue (glycopyrrolate). Thirty-six healthy subjects (18 young--20-38 yrs; 18 older--60-77 yrs) received 4.0 microg/kg i.v. glycopyrrolate. Parotid and submandibular/sublingual saliva samples and xerostomia questionnaire responses were collected. Variables calculated for each subject were: times to initial and maximum suppression and xerostomic complaint; time to recovery; and durations of suppression and complaint. Salivary function was more adversely affected in older persons. There were no consistent age-associated questionnaire response differences. These findings suggest that salivary gland output is more adversely affected by an anti-sialogogue in healthy older vs. younger adults, supporting the secretory reserve hypothesis of salivary function.