To investigate the molecular basis of reduced GLUT-1 concentration of the blood-brain barrier in patients with Alzheimer's disease (AD), the GLUT-1 mass, mRNA content, and structure were studied in eight patients with AD and seven age-matched controls. The results indicate that the 55-kDa GLUT-1 is significantly reduced in AD without a significant change in GLUT-1 mRNA concentrations. Because in some animal models changes in GLUT-1 expression is associated with changes in GLUT-1 mRNA structure, the length of the poly(A) tail of the GLUT-1 mRNA was estimated with a reverse transcription-polymerase chain reaction technique. The length of poly(A) tail of GLUT-1 mRNA in AD subjects was not significantly different from the controls. It is concluded that the AD-related change in GLUT-1 expression is not the result of altered poly(A) length of GLUT-1 mRNA.