Glomerular filtration rate would be decreased by
(a) An increase in the renal blood flow
(b) Compression of the renal capsule
(c) An increase in the afferent arteriolar pressure
(d) Constriction of the efferent arteriole

Options

A. An increase in the renal blood flow
B. Compression of the renal capsule
C. An increase in the afferent arteriolar pressure
D. Constriction of the efferent arteriole

Answer

To determine which option would decrease the glomerular filtration rate (GFR), let's analyze each option step by step:

### Step 1: Understand Glomerular Filtration Rate (GFR)
GFR is the rate at which blood is filtered through the glomeruli in the kidneys. It is influenced by various factors, including blood flow and pressure in the afferent and efferent arterioles.

### Step 2: Analyze Each Option
- **(a) An increase in renal blood flow**: An increase in renal blood flow would typically increase GFR because more blood entering the glomerulus means more fluid can be filtered.

- **(b) Compression of the renal capsule**: Compression of the renal capsule can increase the pressure within the capsule, which may impede the filtration process and potentially decrease GFR.

- **(c) An increase in the afferent arteriolar pressure**: An increase in pressure in the afferent arteriole would lead to increased resistance and reduced blood flow to the glomerulus, ultimately decreasing GFR.

- **(d) Constriction of the efferent arteriole**: Constriction of the efferent arteriole would increase pressure within the glomerulus, which could increase GFR.

### Step 3: Identify the Correct Answer
From the analysis:
- Option (a) increases GFR.
- Option (b) could decrease GFR.
- Option (c) decreases GFR.
- Option (d) increases GFR.

Thus, the correct answer is **(c) An increase in the afferent arteriolar pressure** would decrease the GFR.

### Summary of the Solution
The glomerular filtration rate (GFR) is decreased by an increase in the afferent arteriolar pressure, as this leads to reduced blood flow to the glomerulus and subsequently lowers the filtration rate.

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