Effect of donor age on the concentrations of histatins in human parotid and submandibular/sublingual saliva

Abstract

Histatins are small proteins of human glandular saliva that have antifungal properties. Recent studies show that oral candidal infections increase with age, suggesting an age-associated compromise in oral host defence. Here, the effect of age and of physiological gland stimulation on the concentration and secretion of salivary histatins was investigated. Parotid and submandibular/sublingual salivas were collected from six young adults under unstimulated, mechanical (chewing) and gustatory (0.025 M and 0.1 M citric acid) stimulation, and the concentration and secretion of histatins was measured by cationic polyacrylamide gel electrophoresis with subsequent densitometric scanning of the stained gels. With gland stimulation, parotid saliva showed no significant increase in histatin concentration (μg/ml); however, histatin secretion (μg/min) increased up to 26-fold ( p<0.005; ANOVA). Stimulation of submandibular/sublingual saliva resulted in significant increases in both histatin concentration ( p<0.005) and secretion ( p<0.0005). Ageing effects on salivary histatins were determined in citric acid (0.1 M)-stimulated parotid and submandibular/sublingual saliva samples collected from 80 individuals (divided into four age groups having approximately equal numbers of males and females: 35–44 years; 45–54 years; 55–64 years and 65–76 years). None of the patients was taking medications or wore dentures. ANOVA showed no sex differences in histatins. Regression analysis showed significant age-associated decreases for parotid saliva histatin concentration ( p<0.002) and secretion ( p<0.002) as well as for submandibular/sublingual saliva histatin concentration ( p<0.0001) and secretion ( p<0.0001). Both saliva types showed significant ( p<0.0001) decreases in the histatin concentration per mg of total protein, suggesting a preferential decrease in salivary histatins compared to total salivary protein. These results suggest that the salivary histatin component of the oral host defence system is compromised with increasing age.