The concentration of salt that is isotonic to animal cells is typically around 0.9% (wt/vol) sodium chloride (NaCl). This means that in a saline solution, 0.9 grams of NaCl is dissolved in 100 milliliters of water.
When the salt concentration is isotonic, it means that the solution has the same concentration of solutes as the inside of the animal cells. This balance is crucial because it helps maintain the proper osmotic pressure, preventing the cells from swelling up and bursting, or from shrivelling due to water moving out of the cells.
If the concentration of salt is lower than 0.9%, the solution is considered hypotonic, which can cause water to enter the cells, potentially leading to cell lysis. Conversely, if the concentration is higher than 0.9%, the solution is hypertonic, causing water to leave the cells, resulting in cell shrinkage. Therefore, maintaining a concentration of around 0.9% NaCl is essential for keeping animal cells in a stable environment.