The HCO ions are simultaneously secreted into the blood plasma, thus raising the bicarbonate ion concentration in the plasma, lowering the carbonic acid/bicarbonate ion ratio, and consequently raising the pH of the plasma.
As a result, HCO ions are released into the bloodstream at the same time, resulting in an increase in plasma bicarbonate levels, a decrease in the carbonic acid-to-bicarbonate ratio, and subsequently, an increase in plasma pH.