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Chronic sodium deficit in the immature rat: its effect on adaptation to sodium excess
Insights
Chronic low sodium intake in early development severely stunts growth and affects body sodium balance. Even with repletion, growth recovery is limited, impacting aldosterone levels.
Area of Science:
- Physiology
- Developmental Biology
- Renal Function
Background:
- The effects of chronic low sodium intake during early development on body sodium homeostasis are not well understood.
- Early life nutrition significantly influences long-term health and physiological regulation.
Purpose of the Study:
- To investigate the impact of chronic sodium deficit during early development on growth, sodium balance, and renal function in rats.
- To assess the short-term effects of sodium repletion following a period of sodium restriction.
Main Methods:
- Three groups of rats were subjected to different sodium intake levels during a rapid growth phase (3-7 weeks).
- Sodium repletion was administered during a subsequent phase (8-9 weeks).
- Parameters measured included growth rate, urinary aldosterone excretion, sodium-22 (22Na) volume of distribution, and renal functions.
Main Results:
- Severe growth retardation and reduced 22Na space were observed in rats with the lowest sodium intake (Group III).
- Both moderately and severely restricted groups showed expanded 22Na space and elevated urinary aldosterone post-repletion.
- Despite sodium repletion, the severely restricted group did not achieve catch-up growth.
Conclusions:
- Chronic sodium deficit during early development significantly impairs growth and body sodium regulation.
- Severe sodium restriction leads to persistent growth deficits even after repletion.
- Aldosterone excretion is elevated in response to sodium repletion following deficit, indicating ongoing homeostatic adjustments.
Abstract:
The impact of chronic low-sodium intake during early development on body sodium homeostasis is not sufficiently known. To explore this effect, we have investigated the influence of chronic sodium deficit during the rapid growth period of rats (first phase, age 3-7 wk) and the short-term effect of sodium repletion (second phase, age 8-9 wk) on parameters such as growth rate, urinary aldosterone excretion, 22Na volume of distribution (space), and various renal functions. Three groups were studied: group I (control) and groups II and III. During the first phase the respective sodium intake values for these groups were 8.9, 3.1, and 1.5 meq.kg body wt-1.day-1. During the second phase, all groups had sodium intake of 8.7-8.8 meq.kg body wt-1.day-1. At the end of the first phase, group II showed weight gain and 22Na space values similar to those of group I. Group III demonstrated severe growth retardation and reduced 22Na space. During the second phase, both groups II and III demonstrated expansion of the 22Na space and persistently elevated urinary "acid-labile" aldosterone excretions. Despite the 2 wk of sodium repletion, group III failed to catch up with the body weight of groups I and II. It is concluded that chronic sodium deficit during early development transition is made to a higher sodium intake.