MDCK cells express serotonin-regulable 11beta-hydroxysteroid dehydrogenase type 2.

Area of Science:

• Endocrinology
• Neuroendocrinology
• Renal Physiology

Background:

• Stressful situations activate adrenal and extra-adrenal factors influencing renal 11beta-hydroxysteroid dehydrogenase 2 (11β-HSD2) activity.
• The enzyme 11β-HSD2 protects mineralocorticoid receptors from glucocorticoid overactivation, preventing sodium retention and hypertension.

Purpose of the Study:

• To investigate the role of serotonin as an extra-adrenal factor modulating 11β-HSD2 activity.
• To understand the mechanism by which serotonin influences renal 11β-HSD2 in stressful conditions.

Main Methods:

• Utilized a cell line derived from polarized-epithelium of the distal nephron.
• Assessed 11β-HSD2 activity using 3H-corticosterone as a substrate, with product quantification via HPLC.
• Investigated serotonin's effects at varying concentrations (2nM, 25pM) and substrate levels, employing specific inhibitors (methiothepin, ketanserin).

Main Results:

• Serotonin significantly stimulated 11β-HSD2 activity at specific concentrations (2nM and 25pM).
• The magnitude of serotonin's stimulatory effect was dependent on substrate concentration.
• Inhibitors methiothepin and ketanserin blocked serotonin-induced stimulation of 11β-HSD2 activity.

Conclusions:

• Serotonin acts as a key extra-adrenal factor regulating renal 11β-HSD2 activity.
• Serotonin-mediated catabolic regulation of 11β-HSD2 may prevent mineralocorticoid receptor over-occupancy by elevated glucocorticoids during stress.
• This interaction suggests a potential novel regulatory axis involving serotonin and glucocorticoids in renal physiology.