Regulation of Plasma Renin in Developing Piglets

Plasma renin activity (PRA) was determined in conscious piglets between 1 and 50 days of age before and after treatment with saralasin and indomethacin. Following drug treatment, animals were volume expanded with isotonic saline. Saralasin increased PRA in piglets 1-5 and 18-22 days of age but not 45-50 days. Neither indomethacin nor VE changed PRA at any age. Volume expansion of saralasin- and indomethacin-treated pigs decreased PRA. Neonatal hyperreninemia does not appear to result from renin release stimulated by prostaglandins or by the absence of angiotensin II negative feedback. In addition, the plasma half-life of renin was not different between young and more mature animals suggesting that immature hapatic metabolism of renin cannot be entirely responsible for the high PRA in newborns.