A method to estimate the transient interstitial osmolarity change upon application of osmotic stress in perfused rat submandibular gland.

Transient osmolarity changes in the interstitium of perfused rat submandibular glands were estimated by measurement of the interstitial Cl- concentration ([Cl-]ECF) with an Ag-AgCl electrode upon application of osmotic stress by the addition or subtraction of NaCl. A simple model was used to describe the interstitial osmolarity changes upon the application of osmotic stress. The measured [Cl-]ECF values and interstitial osmolarities were fit well by an exponential function derived from the model. The good fit of the theoretical curve indicates that this model describes adequately the changes in interstitial osmolarity after switching the perfusate osmolarity to a new value.