What are the three main roles of the kidneys in regulating blood pH as described in the chapter?

The three main roles of the kidneys in regulating blood pH are: 1) secreting hydrogen ions into the urine to remove excess hydrogen ions from the blood, thereby increasing blood pH; 2) returning filtered bicarbonate to the blood through tubular reabsorption to sustain the carbonic acid buffer system; and 3) generating new bicarbonate when metabolizing glutamine, which contributes to blood pH regulation.