A baby boy is brought to the hospital because of convulsion. In the course of work up his body temperature & plasma glucose are normal but his CSF glucose is 12 mg/ dl. A possible explanation is

Ans: c (GLUT 1 55K deficiency in capillaries) Ref: Ganong, 22nd ed, p. 615It is a direct pick from self study MCQs in Ganong.According to the given parameters there is deficient transport of glucose across brain capillaries.The predominant GLUT in the brain is GLUT-1 55 K (Ganong p. 615). GLUT-1 45 K is also present in brain capillaries and not in microglia.GLUT 1 - RBC, brain, kidney, placenta, retinaGLUT 2 - Liver, B cells of pancreasGLUT 3 - BrainGLUT 4 - Skin, cardiac muscle, adipose tissueGLUT 5 - Testes, spermsGLUT 7 - Liver, endoplasmic reticulumNote:GLUT 4 is mediated by insulin.GLUT 5 is used as a fructose transporter (semen).