Cryorenin in the newborn human and lamb

Area of Science:

• Neonatal Physiology
• Endocrinology
• Renal Physiology

Background:

• Renin and its precursor, cryorenin, play crucial roles in the renin-angiotensin-aldosterone system.
• Understanding neonatal renin regulation is vital for managing cardiovascular health in infants.

Purpose of the Study:

• To measure renin and cryorenin levels in newborn plasma.
• To investigate the response of these enzymes to angiotensin II infusion in newborn lambs.

Main Methods:

• Plasma renin activity (PRA) was measured in 78 human newborns at birth.
• Six newborn lambs were infused with angiotensin II (0.25 microgram/kg per min) to assess renin and cryorenin levels and blood pressure changes.

Main Results:

• Newborn cord blood showed mean renin levels of 15.9 ng/ml/h and cryorenin levels of 11.1 ng/ml/h.
• Angiotensin II infusion in lambs led to a significant decrease in both cryorenin (from 28.6 to 6.5 ng/ml/h) and renin (from 19 to 15.9 ng/ml/h).
• Aortic blood pressure increased by 30 mm Hg during the infusion.

Conclusions:

• Cryorenin and renin levels are elevated in newborn lambs and humans.
• Both cryorenin and renin are subject to regulation by angiotensin II in the neonatal lamb.
• These findings highlight the importance of the renin-angiotensin system in neonatal cardiovascular regulation.