The effect of carbon dioxide on oxygen-induced retinopathy in the neonatal rat.
OBJECTIVE
Hypercarbia has been suggested as a risk factor for retinopathy of prematurity. We investigated the effect of raised inspired carbon dioxide on oxygen-induced retinopathy in the neonatal rat.


METHODS
Newborn rats raised in expanded litters (n = 25 each) were exposed to cycles of hyperoxia (80% O2) and hypoxia (10% O2 for 7 days, followed by room air recovery for 5 days. During cyclic oxygen exposure, 3 litters (n = 75) were exposed to 10% CO2 (PaCO2 78 mm Hg +/- 6; mean +/- SD) and 3 litters (n = 75) were exposed to 0.2% CO2 (PaCO2 45 mm Hg +/- 7). Animals were sacrificed on day 13 and retinae were analyzed using fluorescein perfusion and ADPase staining techniques.


RESULTS
Neovascularization occurred in 85% of rats exposed to high CO2 compared to 52% of rats exposed to low CO2 (p = 0.001). The severity of neovascularization, in clock hours, was also greater in the rats exposed to high CO2 (p < 0.001).


CONCLUSIONS
Exposure to high CO2 results in an increased incidence and severity of neovascularization in a rat model for oxygen-induced retinopathy. Our results support the suggestion that hypercarbia may be a risk factor for retinopathy of prematurity.
Holmes
J M
JM
Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA.
Zhang
S
S
Leske
D A
DA
Lanier
W L
WL
D000280:Administration, Inhalation; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology*; D015994:Incidence; D009389:Neovascularization, Pathologic / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology; D010100:Oxygen; D051381:Rats; D017207:Rats, Sprague-Dawley; D012164:Retinal Diseases / Q000139:chemically induced* / Q000150:complications*
D002245:Carbon Dioxide; D010100:Oxygen