Question

what role does the sodium-potassium ATPase active transport pump play the series of signals that lead to insulin secretion of pancreatic beta-cells i response to elevated blood glucose levels?

Answer 1

ANSWER:

The Na+/K+ pump with ATPase enzyme is a solute pump that pumps sodium out of cells while pumping potassium into cells, both against their concentration gradients by active transport using ATP to maintain the resting potential. When the glucose level is elevated, it leads to the insulin secretion from pancreatic beta cells. In case of higher glucose level, the extra glucose needs to be transported inside the cell using the sodium gradient. Export of sodium from the cell provides the driving force for several secondary active transporters membrane transport proteins, which import glucose inside. This transported glucose is sensed by the beta cells thus signaling them to release insulin to metabolize the elevated glucose. After glucose has entered the β-cell, it is phosphorylated. Glucose thus finally depolarises the pancreatic β-cell membrane potential by causing reduction in beta cells K⁺ permeability with the aid of initial sodium potassium pump. The depolarized beta cell releases insulin granules which are originally inside the cell and now need to be moved outside with the help of this sodium-potassium gradient. Granules within the cell undergo extensive movement and their secretion results largely from the exocytosis of insulin granules newly recruited to the plasma membrane due to inward movement of glucose. Thus the Insulin granule movement from inside of cell to outside can be stimulated by glucose movement from outside of cell to inside resulting in the phosphorylation of the a-subunits of Na+1,K+1-ATP in response to high extracellular glucose concentration.

Thus in short, the elevated glucose level leads to export of sodium and inward movement to glucose reducing the cells permeabilty for potassium thereby depolarising the beta cell and triggering the release of insulin.