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Catecholamines and phosphate excretion by the remnant kidney
J Isaac1, T J Berndt, V Thothathri
1Department of Physiology, Mayo Clinic and Foundation, Rochester, Minnesota.
Kidney International
|May 1, 1993
Summary
Remnant kidneys show increased phosphate excretion independent of parathyroid hormone. Altered kidney catecholamines, specifically lower norepinephrine and higher dopamine, are linked to this adaptive phosphaturia.
Area of Science:
- Nephrology
- Endocrinology
- Physiology
Background:
- The remnant kidney (RK) demonstrates enhanced fractional excretion of phosphate (FEPi), suggesting parathyroid hormone (PTH)-independent mechanisms.
- Catecholamines, including dopamine (DA) and norepinephrine (NE), play a role in phosphate regulation, with DA being phosphaturic and adrenoreceptor stimulation being antiphosphaturic.
Purpose of the Study:
- To investigate the hypothesis that alterations in renal catecholamine levels in the remnant kidney model are associated with its enhanced phosphaturia.
Main Methods:
- Male Sprague-Dawley rats underwent right nephrectomy and partial left nephrectomy to create a remnant kidney (RK) model.
- Thyroparathyroidectomy (TPTX) was performed, followed by measurements of urinary free dopamine (DA) excretion, glomerular filtration rate (GFR), and fractional excretion of phosphate (FEPi).
- Kidney tissue was analyzed for norepinephrine (NE) and DA concentrations.
Main Results:
- Rats with RK exhibited significantly lower GFR (0.57 vs. 0.83 ml/min/g kidney wt) and significantly higher FEPi (29.4% vs. 8.3%) compared to controls.
- RKs showed significantly lower tissue NE concentrations (85.10 vs. 129.60 ng/g) and significantly higher urinary DA excretion per nephron (0.12 vs. 0.04 pg/min).
Conclusions:
- The remnant kidney model displays PTH-independent phosphaturia.
- Reduced renal norepinephrine and increased urinary dopamine excretion in the RK model may contribute to the observed adaptive phosphaturia.