The Importance of the Carbonate Ion in Physiological Activity.

Abstract

In the course of a study of the response of the guinea pig uterus to pituitrin when the ionic environment of the uterus was varied, the carbonate ion was found to be of importance in determining the magnitude of the response. The carbonate ion seems to exert its influence of itself, and not to be merely reflecting a change in calcium or hydrogen ion activity. This is shown by the following experimental results.

Whenever the carbonate ion activity was increased there was a diminished response of the uterus to pituitrin. This was true whether the carbonate ion activity was increased (a) by increasing the bicarbonate activity and CO₂ tension proportionately so that there was no change in pH; (b) by increasing the bicarbonate activity alone with an increase in pH; or (c) by decreasing the CO₂ tension alone, which also resulted in an increased pH.

Whenever the carbonate ion activity was decreased there was an increased response of the uterus to pituitrin. This occurred whether the carbonate ion activity was decreased (a) by decreasing the bicarbonate ion activity and CO₂, tension proportionately without change in pH; (b) by decreasing the bicarbonate without change in CO₂, tension thereby lowering the pH; or (c) by increasing only the CO₂, tension which also resulted in a decreased pH.

When the carbonate ion activity was kept as CO₂nstant as experimental technique permitted, there was either no change in response or a slight change which might at times be positive and at other times negative. This occurred regardless of whether the bicarbonate was doubled, the CO₂, tension quadrupled and the resulting pH decreased, or the bicarbonate was halved, the CO₂, tension quartered and the resulting pH increased