A central osmosensitive receptor for renal sodium excretion

Area of Science:

• Nephrology
• Neuroscience
• Physiology

Background:

• The brain plays a role in regulating kidney function, including sodium and water balance.
• Understanding how the brain senses and responds to changes in blood composition is crucial for comprehending overall homeostasis.

Purpose of the Study:

• To investigate the impact of increased blood sodium chloride (NaCl) concentration supplied directly to the brain on renal sodium and water excretion.
• To determine if brain receptors sensitive to extracellular tonicity influence kidney function.

Main Methods:

• Conscious, water-loaded sheep underwent intracarotid infusions of hypertonic NaCl (4 M) and compared with intrajugular infusions.
• The effects of intracarotid infusions of hypertonic sucrose or fructose were also assessed.
• Measurements included renal sodium excretion, urine osmolality, and urine flow rate.

Main Results:

• Intracarotid NaCl infusions led to a faster increase in renal sodium excretion and urine osmolality compared to intrajugular infusions.
• Intracarotid sucrose or fructose infusions also significantly increased renal sodium excretion and urine osmolality, while decreasing urine flow.
• These findings indicate a brain-mediated response to changes in blood tonicity.

Conclusions:

• The brain possesses receptors sensitive to extracellular tonicity that modulate renal sodium excretion.
• While changes in antidiuretic hormone (ADH) secretion may contribute to the observed natriuresis, other concurrent mechanisms are also possible.