In the context of renal physiology, the apical membrane of the cells in the cortical collecting tubule is where the exchange of ions with the tubular fluid occurs. Specifically, in a low potassium (K⁺) state, H⁺ ions are exchanged for Na⁺ ions at the apical membrane of the α-intercalated cells. This exchange is facilitated by the H⁺-K⁺ ATPase pump, which is located on the apical membrane. This pump allows H⁺ to be secreted into the tubular lumen in exchange for K⁺ reabsorption, but in a low K⁺ state, Na⁺ can be reabsorbed instead, leading to alkalosis and paradoxical aciduria. The basolateral membrane is typically involved in the transport of ions and molecules between the cell and the blood. For example, Na⁺ is reabsorbed into the blood from the cell via the Na⁺/K⁺ ATPase pump located on the basolateral membrane. Therefore, the exchange of H⁺ for Na⁺ in the context of the cortical collecting tubule should indeed occur at the apical membrane, not the basolateral membrane.
Source: Other - UF COM
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