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Sources of human urinary epinephrine
M G Ziegler1, M Aung, B Kennedy
1Department of Medicine, University of California San Diego, USA. mziegler@UCSD.edu
Kidney International
|January 1, 1997
Summary
The human kidney produces a significant portion of urinary epinephrine (E), not just filtered from blood. Older, heavier hypertensives showed a higher kidney contribution to urinary E levels.
Area of Science:
- Nephrology
- Endocrinology
- Biochemistry
Background:
- The kidney's role in urinary epinephrine (E) excretion is debated, despite evidence of E-synthesizing enzymes in renal tissue.
- Adrenalectomized individuals continue to excrete urinary E, suggesting non-adrenal sources.
Purpose of the Study:
- To quantify the fraction of urinary epinephrine derived directly from the kidney in normal subjects and older, heavier hypertensives.
- To investigate the kinetics of epinephrine in plasma and its clearance into urine.
Main Methods:
- Intravenous infusion of radiolabeled 3H-epinephrine in normal (CON) and older, heavier hypertensive (OHH) subjects.
- Collection of arterial blood and urine samples to measure 3H-E and E levels.
- Analysis of 3H-E kinetics to determine plasma clearance and renal contribution.
Main Results:
- In normal subjects, 43% of urinary E was derived from renal sources, exceeding predicted filtered amounts.
- Older, heavier hypertensives exhibited a significantly higher renal contribution (85%) to urinary E.
- The OHH group produced more urinary E than predicted from plasma clearance, indicating substantial renal synthesis.
Conclusions:
- A major fraction of urinary epinephrine originates from the kidney, not solely from plasma filtration.
- Renal synthesis of epinephrine, potentially via N-methylation of norepinephrine, is a key source of urinary E.
- Understanding renal epinephrine contribution is crucial for interpreting urinary E levels and its potential physiological effects on renal function.