Final answer:
Ingesting hypertonic saline increases plasma osmolality, triggering the release of arginine vasopressin, which promotes water reabsorption and results in increased free water clearance with more concentrated urine.option d.
Step-by-step explanation:
When a healthy 27-year-old man ingests 500 mL of hypertonic saline (5%), he introduces a solution into his body that has a higher concentration of solutes than his body fluids. This condition is known as hypertonicity due to too much solute in his body fluids. The presence of hypertonic saline will increase plasma osmolality, leading to a physiological response to maintain homeostasis.
The hypothalamus detects this increase in osmolality and causes the posterior pituitary gland to secrete arginine vasopressin (also known as antidiuretic hormone or ADH). ADH promotes reabsorption of water in the kidneys, which minimizes water loss and concentrates the urine. Consequently, the most likely laboratory finding is an increased free water clearance, as the kidneys work to clear the excess solute while conserving water, leading to more concentrated urine.