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Effects of age and posture on plasma active renin and plasma inactive renin in normal subjects
1Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei, R.O.C.
Insights
Newborns have higher plasma active and inactive renin levels than adults, regardless of posture. Age influences renin levels in adults, particularly in an upright position.
Area of Science:
- Physiology
- Endocrinology
- Renal Physiology
Background:
- The renin-angiotensin-aldosterone system (RAAS) plays a crucial role in blood pressure regulation.
- Factors like age and posture are known to influence RAAS activity.
- Understanding these influences is vital for interpreting renin measurements.
Purpose of the Study:
- To examine the impact of age and body posture on plasma active renin concentration (ARC) and inactive renin concentration (IRC).
- To compare renin levels between newborns and adults across different positions.
Main Methods:
- Measured plasma ARC and IRC in 81 healthy subjects across five age and posture groups.
- Included newborns (5-day-old, supine) and adults (20-50 and >50 years, supine and upright).
- Quantified ARC via angiotensin I generation and activated IRC using trypsin.
Main Results:
- Plasma ARC and IRC were significantly higher in newborns compared to adults in a supine position.
- In adults, the ratio of ARC to total plasma renin concentration (TPRC) was lower in older adults (>50 years) than younger adults (20-50 years) in a supine position, though not statistically significant.
- Posture appeared to influence renin levels in adults, particularly those over 50.
Conclusions:
- Neonatal renin levels are substantially higher than adult levels.
- Age and posture are significant determinants of plasma renin concentrations in humans.
- Further research is warranted to elucidate the precise mechanisms and clinical implications.
Abstract:
To investigate the effects of age and posture on plasma active and inactive renin, we measured the plasma active renin concentration (ARC) and inactive renin concentration (IRC) in 81 healthy subjects. The subjects were divided into five groups according to age and body position at the time the blood was taken. Group I included 15 five-day-old newborns in a supine position. Group H included 18 adults, aged from 20 to 50 years, who were in a supine position. Group III included 21 adults, over 50 years old, who were in a supine position. Group IV included 20 adults, aged from 20 to 50 years, who were in an upright position. Group V included 19 adults, over 50 years old, who were in an upright position. Twelve subjects were included in Groups II and IV. Plasma active renin was measured by the amount of angiotensin I general when an exogenous renin substrate was added. Plasma inactive renin was activated by trypsin. The results showed that, in a supine position, both ARC and IRC were significantly higher in newborns (Group I) than in the two adult groups (Groups II and III). The mean of the ARC/TPRC (total plasma renin concentration) ratio was lower in adults over 50 years old (Group III) than in those from 20 to 50 years old (Group II), but the difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)