Question

The proteoglycan present in the glomerular basement membrane is?

• A. Keratan sulphate 1
• B. Keratan sulphate 2
• C. Heparan sulphate
• D. Chondroitin sulphate

Hint:

Think of the negatively charged proteoglycan that forms the charge barrier and repels albumin.

Answer 1

The Correct Option is C

Step 1: Recall the layers of the filtration barrier. The glomerular filtration barrier has three parts: the fenestrated capillary endothelium, the glomerular basement membrane (basal lamina), and the podocytes (visceral epithelium of Bowman capsule).
Step 2: Components of the basement membrane. Its key constituents are type 4 collagen, laminin, nidogen (entactin), and proteoglycans. The proteoglycan here is heparan sulphate, so option (c) is correct.
Step 3: Why it matters. Heparan sulphate carries a strong negative charge. This charge-based selectivity helps repel negatively charged plasma proteins such as albumin, contributing to the charge barrier of the glomerulus. Keratan and chondroitin sulphate are not the characteristic proteoglycans here.
Ref: Arvind Arora Review Book of Physiology (p. 371-372).