USMLE Step 1 Question 371

Question:

A 14-year-old boy is brought to the emergency room by his parents. They found him passed out on the floor when coming home from work. They inform you that their son has type 1 diabetes. They also say he has been having a hard time coping with having a chronic disease and has stopped taking his insulin. Which of the following will take up glucose through a high-affinity, insulin-independent transporter?

Correct Answer: D.  Red blood cells

Red blood cells (choice D) take up glucose independent of insulin levels with a high affinity transporter on their cell membrane. The transporter involved is the GLUT-1 transporter and is also found in the endothelial cells of the blood brain barrier.

Adipose tissue (choice A) and skeletal muscle (choice E) both use the GLUT-4 transporter which is insulin dependent. In the presence of insulin, the GLUT-4 transporter is released from intracellular storage sites to the cell membrane to facilitate passive diffusion of glucose into the cell.

Kidney cells (choice B) and liver cells (choice C) both contain GLUT-2 transporters. Although this is also an insulin-independent transporter, it is a high capacity, low affinity transporter.