Ferraris R P, Hsiao J, Hernandez R, Hirayama B
Department of Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark 07103-2714.
Am J Physiol. 1993 Feb;264(2 Pt 1):G285-93. doi: 10.1152/ajpgi.1993.264.2.G285.
To evaluate the effect of age on nutrient transport, the absorption rates of D-glucose, D-fructose, L-alanine, L-aspartate, L-leucine, L-lysine, L-proline, folic acid, and nicotinamide were determined in isolated jejunal tissues of young (6.7 mo old) and aged (23.7 and 27.0 mo old) mice (COBS:SFW). D-Glucose and D-fructose uptakes per milligram tissue were approximately 20-120% higher in the proximal jejunum and 15-50% higher in the distal jejunum of young mice. Amino acid and vitamin uptakes per milligram were also higher in young mice, but differences were not statistically significant. The number of Na(+)-D-glucose transporters per milligram tissue as estimated by specific phlorizin binding decreased with age. There was no age-related change in passive L-glucose permeability, in Kd of specific phlorizin binding, in transporter turnover rate, and in the molecular weight of the Na(+)-D-glucose transporter. Thus a reduction in D-glucose transporter site density fully accounts for the age-related decline in D-glucose transport rate per milligram small intestine.
为评估年龄对营养物质转运的影响，测定了幼年（6.7月龄）和老年（23.7和27.0月龄）小鼠（COBS:SFW）离体空肠组织中D-葡萄糖、D-果糖、L-丙氨酸、L-天冬氨酸、L-亮氨酸、L-赖氨酸、L-脯氨酸、叶酸和烟酰胺的吸收率。每毫克组织的D-葡萄糖和D-果糖摄取量在幼年小鼠的空肠近端约高20 - 120%，在空肠远端约高15 - 50%。每毫克组织的氨基酸和维生素摄取量在幼年小鼠中也较高，但差异无统计学意义。通过特异性根皮苷结合估计的每毫克组织中Na(+)-D-葡萄糖转运体数量随年龄下降。被动L-葡萄糖通透性、特异性根皮苷结合的解离常数、转运体周转率以及Na(+)-D-葡萄糖转运体的分子量均无年龄相关变化。因此，D-葡萄糖转运体位点密度的降低完全解释了每毫克小肠中与年龄相关的D-葡萄糖转运速率下降。
