 After a tissue specimen has been obtained, it must be surrounded or perfused by a solution at an appropriate temperature containing the salts and nutrients required to keep the cells alive.This may be performed by simply submerging the tissue in the solution, or may involve more complex arrangements such as Langendorff perfusion.Commonly used solutions included modifications of Tyrode's solution or Krebs and Henseleit's solution These solutions contain precise concentrations of electrolytes including sodium, potassium, calcium, magnesium, phosphate, chloride, and glucose.