In experimental studies of glomerular filtration, dextrans—complex branched polysaccharides—serve as ideal markers to understand how molecular size and charge influence filtration through the kidney’s glomerulus. Investigations often include neutral, polyanionic (negatively charged), and polycationic (positively charged) dextrans with varying molecular radii.

Key Findings in Dextran Filterability

1. Size Matters:
   Smaller dextrans have higher filterability than larger ones. The glomerular filtration barrier restricts larger molecules more effectively due to physical pore size limitations. This corresponds with statement (A), which is widely supported by research.pubmed.ncbi.nlm.nih

2. Charge Influence:
   The filtration barrier is negatively charged, largely due to the glycosaminoglycan-rich glomerular basement membrane and podocyte slit diaphragm components.

   • Neutral dextrans tend to filter more readily than charged ones.

   • Polyanionic dextrans, being negatively charged, face electrostatic repulsion and show lower filterability than neutral counterparts.

   • Polycationic dextrans, carrying positive charges, are attracted to the negatively charged filtration barrier, but this can limit movement, often resulting in decreased filterability compared to neutrals. Hence, polycationic dextrans are not typically filtered better than neutral dextrans.sciencedirect

3. Summary of Charge Effects:

   • Neutral > Polycationic ≥ Polyanionic in filterability—neutral dextrans are filtered most, polyanionic the least.

   • Statement (B) is correct, and statement (D) that polyanionic dextrans filter more is incorrect.

   • Statement (C) that polycationic filter more than neutral dextrans is incorrect.

Correct Combination from the Choices

• Statement (A) (small size favors filterability) is true.

• Statement (B) (neutral dextrans filter more than charged ones) is true.

• Statement (C) and (D) are false based on charge effects and known electrostatic interactions.

Therefore, the correct choice aligns with (1) (A) only or (2) (B) only—however, as both (A) and (B) are supported, but only options with single statements or (A) and (C) together are given, the best answer is:

(1) (A) only

because size is the primary determinant, and charge effects, while important, are not completely accounted for in the other combinations provided.

Conclusion

• Smaller dextran molecules have greater glomerular filterability.

• Neutral dextrans filter better than both polyanionic and polycationic ones.

• Polycationic dextrans do not filter more than neutral dextrans.

• Polyanionic dextrans are filtered least due to negative charge repulsion.

Correct Answer: (1) (A) only

This reflects the dominant role of size and partially the charge in glomerular permeability.

The correct answer is:pubmed.ncbi.nlm.nih+1

(1) (A) only

Explanation:

• (A) Dextrans with smaller diameter have greater filterability than larger dextrans, which is true because size significantly influences filtration through the glomerulus.

• (B) Neutral dextrans filter more than polyanionic and polycationic is partially true but not entirely consistent with the other options.

• (C) Polycationic dextrans filter more than neutral and polyanionic is incorrect, as positive charges tend to interact with the negatively charged glomerular barrier but do not increase filterability more than neutral.

• (D) Polyanionic dextrans filtering more than others is incorrect because negative charges repel the negatively charged filtration barrier, reducing filterability.