Functional mediation of compensatory enlargement of the parotid gland.

The role of functional activity in mediating compensatory enlargement of the parotid gland after removal of the other major salivary glands was investigated. Increased levels of activity were achieved by feeding rats a bulk diet. Conversely, a liquid diet was used to reduce the functional demands on the parotid. It was found that the liquid diet completely prevented the compensatory response from occurring. Bulk diet, on the other hand, caused an even greater compensatory response than did the standard chow diet. Compensatory enlargement of the parotid, therefore, depends on its functional activity and not on other, e.g., humoral factors dissociated from function. The character of the cellular response in compensatory enlargement was also examined. The chow diet caused compensatory enlargement by an increase in cell size with little, if any, increase in cell number.