Final answer:
The cortical collecting tubule is regulated by ADH, aldosterone, and renin as part of the renin-angiotensin-aldosterone system. ADH directly influences water recovery, while aldosterone stimulates sodium uptake, affecting water reabsorption. Renin initiates the system that ultimately influences this tubule's function.
Step-by-step explanation:
Regulation of the cortical collecting tubule is multifaceted and involves several hormones. ADH (Antidiuretic Hormone) powerfully influences water recovery by stimulating the insertion of aquaporin water channels into the cell membranes of the collecting ducts.
Aldosterone, on the other hand, specifically stimulates the uptake of sodium (Na+) at the apical cell membrane of cells in the distal convoluted tubule (DCT) and the collecting ducts, positively affecting water reabsorption since water follows the osmotic gradient created by Na+ reabsorption.
Even though renin itself is not a hormone, but an enzyme, it initiates the renin-angiotensin-aldosterone system (RAAS) by converting angiotensinogen to angiotensin I, which eventually leads to an increase in aldosterone and thereby influences the kidney function as well. Considering these functions, it is clear that the correct answer to the question is '4) All of the above' as ADH, aldosterone, and renin all play a role in regulating the cortical collecting tubule.