Final answer:
The expected outcome from infusing 2 L of normal saline in a healthy person is decreased renin secretion due to increased blood volume and pressure.
Step-by-step explanation:
If a healthy person receives 2 L of normal saline, which has a sodium chloride concentration similar to that of plasma, the expected physiological response is decreased renin secretion.
Normal saline administration would increase blood volume, which in turn would increase blood pressure. Higher blood pressure detected by the baroreceptors would result in a negative feedback response leading to decreased sympathetic outflow to the kidneys.
This decrease in sympathetic stimulation would lead to the dilatation of the afferent arterioles of the glomerulus, increasing glomerular filtration rate (GFR) and promoting diuresis.
Additionally, the increase in blood volume and pressure would suppress renin release from the juxtaglomerular apparatus of the kidneys, thus reducing the conversion of angiotensinogen to angiotensin I and ultimately the formation of angiotensin II.
With less angiotensin II, there would be a reduced stimulus for aldosterone secretion from the adrenal cortex. Aldosterone normally promotes the reabsorption of sodium (and therefore water) in the nephron.
Which in the presence of normal saline infusion is not favored. Therefore, the typical physiological response includes an increased diuresis and maintainence of sodium balance, avoiding high plasma concentration of sodium.