Effect of postnatal intermittent hypoxia on growth and cardiovascular regulation of rat pups.
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.


OBJECTIVE
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.


CONCLUSIONS
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.
Division of Neonatology, Department of Pediatrics, Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, Ohio 44106-6010, USA.
M E
ME
Pozo
A
A
Cave
O A
OA
Köroğlu
D G
DG
Litvin
R J
RJ
Martin
J
J
Di Fiore
P
P
Kc
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001794:Blood Pressure; D002319:Cardiovascular System / Q000254:growth & development / Q000294:innervation / Q000503:physiopathology*; D004195:Disease Models, Animal; D006130:Growth Disorders / Q000209:etiology* / Q000503:physiopathology; D006339:Heart Rate; D000860:Hypoxia / Q000150:complications* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D015430:Weight Gain