Final answer:
The correct answer is option d. The juxtaglomerular cells release renin, which is crucial for maintaining blood pressure and fluid balance through the renin-angiotensin system. Renin converts angiotensinogen to angiotensin I, which is then converted to angiotensin II, leading to the release of aldosterone and ADH and consequently stabilizing blood pressure.
Step-by-step explanation:
Juxtaglomerular Cells and Renin Secretion
The substance released by juxtaglomerular cells is renin. These cells are part of the juxtaglomerular complex located in the kidneys. Renin is an important enzyme that plays a pivotal role in the body's renin-angiotensin system (RAS), which regulates blood pressure and fluid balance. When blood pressure falls, the juxtaglomerular cells release renin into the bloodstream.
Renin then acts on angiotensinogen, a protein produced by the liver, converting it to angiotensin I. Subsequently, angiotensin I is converted to angiotensin II by the enzyme angiotensin-converting enzyme (ACE). Angiotensin II has multiple effects: it stimulates the release of aldosterone from the adrenal glands and antidiuretic hormone (ADH) from the pituitary gland, ultimately leading to water retention and increased blood volume, which helps stabilize blood pressure.
As a side note, alcohol can increase urine output because it inhibits the secretion of ADH, leading to less water reabsorption in the kidneys and thus more urine production.