Cortisol binding in uremic plasma. II. Decreased cortisol binding to albumin

Area of Science:

• Endocrinology
• Nephrology
• Biochemistry

Background:

• Patients with chronic renal failure often show elevated free cortisol levels.
• Previous studies suggest potential binding abnormalities of plasma proteins contributing to this phenomenon.

Purpose of the Study:

• To investigate cortisol binding to albumin in uremic plasma.
• To determine if altered protein binding explains increased free cortisol in chronic renal failure.

Main Methods:

• Equilibrium dialysis was used to measure unbound and albumin-bound cortisol fractions.
• Heat inactivation of corticosteroid-binding globulin was employed.
• Uremic and non-uremic plasma samples were compared.

Main Results:

• A significantly lower ratio of albumin-bound to unbound cortisol was observed in uremic plasma compared to non-uremic plasma (p < 0.05).
• Treatment of uremic plasma with dextran-activated charcoal normalized the cortisol binding ratio.
• The identified substance affecting binding is heat-stable and removed by charcoal.

Conclusions:

• Cortisol binding to albumin is decreased in uremic plasma.
• A heat-stable substance, removable by charcoal, is responsible for this reduced binding.
• These findings offer insight into the altered cortisol metabolism in chronic renal failure.