Regulation of plasma renin in developing piglets

Area of Science:

• Physiology
• Neonatal Development
• Renal System

Background:

• Neonatal hyperreninemia, characterized by elevated plasma renin activity (PRA), is observed in newborns.
• The underlying mechanisms contributing to this phenomenon remain incompletely understood.

Purpose of the Study:

• To investigate the factors contributing to elevated plasma renin activity (PRA) in neonatal piglets.
• To determine the roles of prostaglandins and angiotensin II feedback in neonatal hyperreninemia.
• To assess the influence of renin metabolism on PRA in developing piglets.

Main Methods:

• Plasma renin activity (PRA) was measured in conscious piglets aged 1 to 50 days.
• Animals were treated with saralasin (angiotensin II receptor blocker) and indomethacin (prostaglandin inhibitor).
• Volume expansion with isotonic saline was performed following drug treatments.

Main Results:

• Saralasin increased PRA in piglets aged 1-5 and 18-22 days, but not in older piglets (45-50 days).
• Indomethacin and volume expansion alone did not alter PRA at any age.
• Volume expansion in saralasin- and indomethacin-treated pigs led to a decrease in PRA.
• The plasma half-life of renin was consistent across different age groups.

Conclusions:

• Neonatal hyperreninemia in piglets does not appear to stem from renin release stimulated by prostaglandins or a lack of angiotensin II negative feedback.
• Immature hepatic metabolism of renin is unlikely to be the sole cause of high PRA in newborns.
• These findings suggest alternative regulatory mechanisms for renin-angiotensin system development in neonates.