Neural and extraneural catecholamine production by rat kidneys

Area of Science:

• Nephrology
• Neuroendocrinology
• Physiology

Background:

• The kidney's role in catecholamine production and regulation is complex.
• Innervation of the kidney suggests a direct neural influence on its function.

Purpose of the Study:

• To quantify catecholamine (norepinephrine, epinephrine, dopamine) production by innervated and denervated kidneys.
• To determine the contribution of renal nerves to catecholamine efflux in various bodily fluids.

Main Methods:

• Radioenzymatic assay was used to measure norepinephrine (NE), epinephrine (E), and dopamine (DA) levels.
• Measurements were taken in lymph, urine, arterial plasma, and renal venous plasma of hydropenic rats.
• Comparisons were made between innervated and denervated kidney preparations.

Main Results:

• Denervation reduced NE excretion in urine by 18% and NE/DA efflux in renal venous plasma by 37%/30%.
• Renal nerves contributed significantly to NE efflux, but only half of DA efflux originated from renal nerves.
• Epinephrine handling by the kidney was unaffected by denervation.

Conclusions:

• Renal nerves are a source of both norepinephrine and dopamine.
• A significant portion of dopamine efflux originates from extraneuronal sources within the kidney.
• Renal lymph catecholamine levels suggest low peritubular concentrations except in specific renal clefts.