Question

What effect does ADH have at the collecting duct apical membrane? Basolateral?

a. Apical - increase permeability to water; Basolateral - activate GPCRs, adenylyl cyclase.
b. Apical - decrease permeability to water; Basolateral - inhibit GPCRs, adenylyl cyclase.
c. Apical - increase permeability to sodium; Basolateral - decrease GPCR activity.
d. Apical - enhance active transport of glucose; Basolateral - activate ion channels.

Answer 1

ADH increases water permeability at the collecting duct apical membrane, resulting in more concentrated urine. ADH activates GPCRs and adenylyl cyclase at the basolateral membrane, aiding in the insertion of aquaporin channels.

Step-by-step explanation:

Effect of ADH at the Collecting Duct Apical Membrane:

When stimulated by ADH, aquaporin channels are inserted into the apical membrane of principal cells, which line the collecting ducts. This increases the water permeability of the cells, allowing water to be pulled from the collecting duct into the surrounding interstitial space and peritubular capillaries. As a result, the final urine becomes more concentrated.

Effect of ADH at the Collecting Duct Basolateral Membrane:

At the basolateral membrane, ADH activates GPCRs (G-protein coupled receptors) and adenylyl cyclase. This signaling pathway helps regulate the insertion of aquaporin channels into the apical membrane, enhancing water reabsorption.