Final answer:
Plasma carbon dioxide levels have a direct relationship with renal secretion and excretion of hydrogen ions. Carbon dioxide in the plasma combines with water to form carbonic acid which dissociates into hydrogen ions and bicarbonate ions. The hydrogen ions are secreted into the filtrate in the kidneys and the bicarbonate ions are returned to the blood.
Step-by-step explanation:
Plasma carbon dioxide levels have a direct relationship with renal secretion and excretion of hydrogen ions. When carbon dioxide is available in the plasma, it can combine with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate ions. The hydrogen ions are then secreted into the filtrate in the kidneys and can be reabsorbed as part of new water molecules or eliminated in the urine. The bicarbonate ions return to the blood through peritubular capillaries.