The actions of cortisol on fetal renal function

Area of Science:

• Perinatal Physiology
• Renal Physiology
• Endocrinology

Background:

• Fetal kidney development and maturation are critical for postnatal adaptation.
• The role of glucocorticoids in modulating fetal renal function is not fully understood.

Purpose of the Study:

• To investigate the effects of cortisol administration on renal function in late-gestation fetal sheep.
• To determine how cortisol influences glomerular filtration, renal blood flow, and electrolyte handling in the immature kidney.

Main Methods:

• Renal function was assessed in 6 fetal sheep (126-135 days gestation).
• Cortisol (15 mg) was administered intramuscularly three times at 12-hour intervals.
• Measurements included renal blood flow, glomerular filtration rate, urine flow, and electrolyte excretion before and after cortisol treatment.

Main Results:

• Cortisol significantly increased renal blood flow (P < 0.05), glomerular filtration rate (P < 0.005), and urine flow rate (P < 0.02).
• Bicarbonate and phosphate excretion increased, while titratable acid excretion also rose.
• Sodium reabsorption shifted from the proximal tubule to the distal tubule, with increased distal fractional sodium reabsorption (P < 0.01).

Conclusions:

• Cortisol enhances fetal sheep renal function, increasing glomerular filtration and altering sodium handling.
• These effects suggest cortisol plays a role in preparing the immature kidney for fluid and electrolyte homeostasis after birth.
• Increased delivery of sodium and water to the distal nephron allows for regulated reabsorption based on the neonate's needs.