19-nor-DOC biosynthesis in the isolated perfused rat kidney

Area of Science:

• Endocrinology
• Renal Physiology
• Steroid Metabolism

Background:

• 19-nor-deoxycorticosterone (19-nor-DOC) is a potent mineralocorticoid with salt-retaining and hypertensive properties.
• While its precursor, 19-oxo-DOC, is synthesized in the adrenal cortex, the site of conversion to 19-nor-DOC remained unknown.
• Previous research indicated that 19-nor-DOC is excreted in urine, suggesting extra-adrenal production.

Purpose of the Study:

• To investigate the hypothesis that the kidney is involved in the synthesis of 19-nor-DOC from adrenal precursors.
• To determine if the kidney possesses the enzymatic machinery to convert 19-oxo-DOC into 19-nor-DOC.

Main Methods:

• Isolated rat kidney preparations were utilized for perfusion studies.
• 19-oxo-DOC, a known precursor of 19-nor-DOC, was added to the kidney perfusate at a concentration of 10 microM.
• The perfusion was conducted for a duration of 1 hour.

Main Results:

• The kidney preparations demonstrated significant conversion of 19-oxo-DOC.
• Approximately 71% of the precursor was converted to 19-oic-DOC, an immediate precursor to 19-nor-DOC.
• A notable 8.3% of the precursor was directly converted to 19-nor-DOC.

Conclusions:

• This study provides the first definitive evidence that the kidney synthesizes 19-nor-DOC.
• The kidney plays a crucial role in the extra-adrenal conversion of adrenal precursors into the potent mineralocorticoid 19-nor-DOC.
• These findings have implications for understanding mineralocorticoid metabolism and hypertension.