Which of the following causes increase in both GFR and renal plasma flow?
## Core Concept
The question tests the understanding of renal physiology, specifically the regulation of Glomerular Filtration Rate (GFR) and renal plasma flow (RPF). GFR is the rate at which fluid filtered by the glomeruli flows into Bowman's space, while RPF is the rate of plasma flow through the renal circulation. Both are crucial for kidney function and are influenced by various factors including changes in blood pressure, sympathetic nervous system activity, and certain drugs.
## Why the Correct Answer is Right
The correct answer, . **Adequate hydration** or increased fluid intake leads to an increase in blood volume, which in turn increases renal blood flow. This increase in renal blood flow results in an increase in both renal plasma flow (RPF) and glomerular filtration rate (GFR). The increase in GFR is due to the increased hydrostatic pressure within the glomerular capillaries, which enhances the filtration of fluid from the blood into Bowman's space.
## Why Each Wrong Option is Incorrect
- **Option A:** **Sympathetic stimulation** typically decreases both GFR and RPF by causing vasoconstriction of the renal arteries, thereby reducing blood flow to the kidneys. This is a stress response that prioritizes blood flow to muscles and brain over the kidneys.
- **Option B:** **NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)** can decrease GFR by inhibiting prostaglandin synthesis, which is important for maintaining renal blood flow, especially in states of low renal perfusion. They do not increase RPF.
- **Option C:** **ACE inhibitors** can decrease GFR in certain conditions by reducing angiotensin II levels, which normally helps to maintain glomerular pressure. They can also slightly decrease or have a variable effect on RPF.
## Clinical Pearl / High-Yield Fact
A key point to remember is that an increase in GFR is often seen with increased fluid intake or **adequate hydration**, which is essential for maintaining optimal kidney function. Conversely, dehydration can significantly decrease GFR. This concept is critical in clinical settings, especially when managing patients with renal issues.
## Correct Answer Line
**Correct Answer: .**