If a toxin disrupted the Na+/K+ pump so that intracellular sodium rose substantially while intracellular potassium fell, which immediate cellular effect would you predict?

• A. Water would immediately leave cells, causing cell shrinkage, because the pump failure increases intracellular negative charge and repels water molecules out of the membrane.
• B. A long-term increase in extracellular potassium concentration would occur instantaneously, producing immediate vasoconstriction in surrounding capillaries.
• C. Water would flow into cells by osmosis and cells would swell because intracellular osmolarity increased from the extra sodium present.
• D. Cells would maintain normal volume because the leak channels would compensate fully for pump failure and keep gradients unchanged for several hours.

Answer: (C)