Renomedullary Interstitial Cell Endothelin A Receptors Regulate BP and Renal Function

Area of Science:

• Physiology
• Nephrology
• Endocrinology

Background:

• The physiological role of renomedullary interstitial cells in the renal inner medulla is largely unknown.
• Endothelin A receptors influence renomedullary interstitial cell function in vitro.

Purpose of the Study:

• To investigate the in vivo effects of targeting renomedullary interstitial cell endothelin A receptors.
• To generate and study a mouse model with inducible disruption of these receptors.

Main Methods:

• Created a mouse model with inducible knockout of endothelin A receptors in renomedullary interstitial cells at 3 months of age.
• Assessed blood pressure and renal function under varying salt and water intake conditions.
• Analyzed urinary excretion of sodium, potassium, water, endothelin-1, nitrite/nitrate, and PGE2.
• Measured expression of nitric oxide synthase-1, cyclooxygenase-1, epithelial sodium channel, cyclooxygenase-2, and aquaporin-2.

Main Results:

• On a high-salt diet, knockout mice showed reduced blood pressure, increased urinary salt and water excretion, and altered expression of nitric oxide and prostaglandin pathways.
• Water-loaded knockout mice exhibited enhanced urine volume and reduced urine osmolality.
• No evidence of endothelin-1-induced renomedullary interstitial cell contraction was observed.

Conclusions:

• Disrupting renomedullary interstitial cell endothelin A receptors reduces blood pressure and enhances salt/water excretion.
• This is associated with increased production of intrinsic renal natriuretic and diuretic factors.
• Renomedullary interstitial cells can modulate blood pressure and renal function under physiological conditions.