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Effect of postnatal intermittent hypoxia on growth and cardiovascular regulation of rat pups
M E Pozo1, A Cave, O A Köroğlu
1Division of Neonatology, Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, Ohio 44106-6010, USA.
Insights
Repetitive intermittent hypoxia (IH) in early life impacts growth and cardiovascular regulation in rat pups. A clustered IH pattern significantly lowered blood pressure long-term, while both patterns reduced heart rate.
Area of Science:
- Neonatal physiology
- Cardiovascular regulation
- Developmental biology
Background:
- Intermittent hypoxia (IH) is common in preterm infants, but its long-term effects on growth and cardiovascular health are not fully understood.
- The pattern of hypoxia-reoxygenation may influence these outcomes.
Purpose of the Study:
- To investigate if clustered versus dispersed patterns of IH in early postnatal life cause different long-term changes in growth and cardiovascular regulation.
- To test the hypothesis of differential long-term alterations induced by IH patterns.
Main Methods:
- Rat pups were exposed to room air or two IH patterns (clustered/dispersed) from day 1 to 7.
- Body weight was monitored daily for 8 days and weekly up to 8 weeks.
- Noninvasive blood pressure and heart rate measurements were taken weekly from weeks 4 to 8.
Main Results:
- Both IH patterns caused initial growth restriction, followed by catch-up growth by week 3 post-exposure.
- IH exposure led to a sustained decrease in heart rate irrespective of the pattern.
- Arterial pressure showed differential effects: clustered IH significantly lowered blood pressure, while dispersed IH had no effect compared to controls.
Conclusions:
- Repetitive IH during a critical developmental window induces lasting changes in cardiovascular regulation.
- These changes may involve prolonged alterations in sympathovagal balance, regardless of the specific IH pattern.
Background:
Intermittent hypoxic episodes are common among preterm infants, although longer term consequences on growth pattern and cardiovascular regulation are unclear. Furthermore, the effects of intermittent hypoxia (IH) may depend on the pattern of hypoxia-reoxygenation.
Objectives:
We tested the hypothesis that a clustered versus dispersed pattern of repetitive IH during early postnatal life would induce differential long-term alteration in growth and cardiovascular regulation.
Methods:
Sprague-Dawley rat pups were exposed to room air or to one of two patterns of IH (clustered vs. dispersed) from 1 to 7 days of life. Body weight was measured daily for the first 8 days and weekly from weeks 2 to 8. Blood pressure (BP) and heart rate were measured weekly from weeks 4 to 8 using a noninvasive tail-cuff method for awake, nonanesthetized animals.
Results:
Exposure to both patterns of repetitive IH induced early growth restriction followed by later catch-up of growth to controls 3 weeks after completion of IH exposures. IH-exposed rats exhibited a sustained decrease in heart rate regardless of the hypoxic exposure paradigm employed. In contrast, a differential response was seen for arterial pressure; the clustered paradigm was associated with a significantly lower BP versus controls, while the pups exposed to the dispersed paradigm showed no effect on BP.
Conclusion:
We speculate that repetitive IH during a critical developmental window and regardless of IH exposure paradigm contributes to prolonged changes in sympathovagal balance of cardiovascular regulation.
