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Behaviour of plasma renin activity and aldosterone during the first 72 h of life
Insights
Newborns show elevated plasma renin activity and plasma aldosterone concentrations in the first 72 hours of life. These levels increase over the first three days, with potential contributing factors still under investigation.
Area of Science:
- Neonatal physiology
- Endocrinology
- Renal physiology
Background:
- The renin-angiotensin-aldosterone system (RAAS) plays a crucial role in cardiovascular and electrolyte homeostasis.
- Understanding RAAS activity in newborns is essential for assessing their physiological adaptation to extrauterine life.
Purpose of the Study:
- To measure plasma renin activity (PRA) and plasma aldosterone concentrations (PAC) in normal newborns during the first 72 hours of life.
- To investigate potential correlations between PRA, PAC, and serum electrolytes in this population.
Main Methods:
- Blood samples were collected from fifty normal newborns within the first 72 hours of life.
- Plasma renin activity (PRA) and plasma aldosterone concentrations (PAC) were quantified.
- Serum sodium and potassium levels were analyzed.
Main Results:
- Elevated PRA was observed in all newborns, with a trend of increasing levels from day 1 to day 3.
- Elevated PAC also increased significantly from day 1 to day 3.
- No significant correlation was found between PRA and PAC.
- Serum sodium was normal, while serum potassium was slightly elevated in the first 48 hours.
Conclusions:
- Newborns exhibit high and increasing levels of PRA and PAC during the initial postnatal period.
- The precise physiological significance of these elevated RAAS components remains unclear.
- Potential contributing factors include low blood pressure, macula densa hypersensitivity, immature renal response to aldosterone, and hyperkalemia.
Abstract:
Plasma renin activity (PRA) and plasma aldosterone concentrations (PAC) were determined in fifty normal newborns during the first 72 h of life. PRA was elevated in all cases and tends to increase from the first (6.79 +/- 0.69SE ng/ml/h) to the third day of life (8.24 +/- 0.96SE ng/ml/h). PAC was also elevated and rose from 24.06 +/- 3.23SE ng/dl on the first day to 39.20 +/- 4.25SE ng/dl on the third day. No significant correlation was observed between PRA and PAC. Serum sodium was within the normal range, whereas serum potassium was slightly elevated during the first 48 h of life. The physiological significance of the high levels of PRA and PAC in newborns is not clear at present. Many factors may be involved in the increased activation of the renin-angiotensin-aldosterone system: low blood pressure, hypersensitivity of the macula densa to catecholamines, relative insensitivity of the immature kidney to aldosterone, hyperkalaemia and other control mechanisms for aldosterone secretion all of which probably operate simultaneously during the first days of life.