Interrelations between binding affinity and metabolic clearance rate for the main corticosteroids in the rabbit

Area of Science:

• Endocrinology
• Pharmacology
• Biochemistry

Background:

• Corticosteroids are crucial hormones with varying metabolic clearance rates (MCRs).
• Transcortin is a key binding protein for corticosteroids, influencing their metabolism and availability.
• Understanding factors affecting corticosteroid MCR is vital for physiological and pharmacological studies.

Purpose of the Study:

• To investigate the relationship between corticosteroid binding affinity and metabolic clearance rate in rabbits.
• To determine the protective role of transcortin and specific antibodies against corticosteroid metabolism.

Main Methods:

• Measurement of metabolic clearance rates (MCRs) for various corticosteroids in rabbits.
• In vitro assessment of relative binding affinities of transcortin to different corticosteroids.
• Induction of antibodies against specific corticosteroids and evaluation of their impact on MCR.

Main Results:

• Corticosterone exhibited a higher MCR than cortisol in rabbits.
• Transcortin binding affinity decreased in the order: cortisol > cortisone > corticosterone > 11-dehydrocorticosterone > aldosterone.
• Antibodies against aldosterone, corticosterone, or cortisone significantly reduced their respective MCRs.

Conclusions:

• Corticosteroid MCR in rabbits is directly correlated with its binding to specific proteins.
• Rabbit transcortin, despite high corticosterone binding affinity, offers limited protection against peripheral metabolism.
• Specific antibodies with high binding affinity provide effective protection against corticosteroid metabolism in rabbits.