isotonic

A solution with identical osmotic pressure or tonicity with plasma or interstitial fluid. This results in no net flow of water across semipermeable membranes. Thus bathing cells in culture within an isotonic solution result in no water diffusion into ot out of the cells across the cell membrane. Normal saline is isotonic with normal plasma. Also see unrelated isotonic training.

Related

isotonic training osmotic pressure

References

Dorland's Medical Dictionary, 23rd ed., WB Saunders, Philadelphia, 1990