New indicator of small intestinal ageing in senescence-accelerated mice.

Aging is understood to be a time-dependent decline in various physiological functions. Motor and sensory functions deteriorate relatively early after maturity, while nutrient absorption and barrier functions in the digestive tract are reported to decline later, but the specific sites and mechanisms remain unclear. Senescence-Accelerated Mouse Prone 1 (SAMP1) mice (9 months) and C57BL/6 mice (over 19 months) were used to examine age-related changes in intestinal function of different regions using Ussing chambers. In SAMP1 mice, nutrient absorption and tight junction cationic permeability were reduced, while barrier function was enhanced in the middle and distal small intestine. Similar functional declines were observed in the distal small intestine of aged C57BL/6 mice. These findings suggest that the effect of aging is first observed in the distal small intestine, and that cation selectivity of the epithelial intercellular tight junction could serve as a new indicator for aging and functional evaluation index.