GLOSSARY

The proximal convoluted tubule, or PCT, is the first and longest tubular part of the nephron, lying in the renal cortex right after Bowman’s capsule. It carries out the greatest amount of reabsorption in the nephron.

Structure

PCT cells are cuboidal with a brush border (many microvilli), which greatly increases the absorptive surface. They contain many mitochondria, because active reabsorption needs a lot of ATP.

Reabsorption

• Water and sodium: about 65 percent; water reabsorption is isosmotic and occurs through aquaporin-1.
• Glucose: almost 100 percent, via SGLT2 and SGLT1.
• Amino acids: almost 100 percent.
• Bicarbonate: about 80–90 percent.
• Potassium, calcium, phosphate and filtered small proteins.

Secretion