Related Experiment Videos
Antioxidant enzyme responses to hyperoxia in preterm and term rats after prenatal dexamethasone administration
S E Keeney1, M J Mathews, D K Rassin
1Department of Pediatrics, University of Texas Medical Branch, Galveston 77550.
Insights
Prenatal dexamethasone boosts survival and antioxidant enzyme activity in preterm rat pups at birth. However, this effect on antioxidant enzymes diminishes after postnatal hyperoxia exposure.
Area of Science:
- Biochemistry
- Neonatal Physiology
- Pharmacology
Background:
- Prenatal steroid therapy is known to improve fetal lung maturation.
- The impact of prenatal steroids on the neonatal antioxidant system post-birth remains unclear.
- Antioxidant enzymes are crucial for protecting against oxidative stress.
Purpose of the Study:
- To investigate the effects of prenatal dexamethasone on antioxidant enzyme activities in preterm and term rat pups.
- To assess the impact of postnatal hyperoxia on these enzyme activities.
- To determine if prenatal dexamethasone offers lasting protection to the antioxidant system.
Main Methods:
- Prenatal dexamethasone or saline treatment in rat dams.
- Measurement of catalase, superoxide dismutase, and glutathione peroxidase activities in lung homogenates.
- Enzyme activity assessment at birth and after hyperoxic ( >98% oxygen) exposure.
Main Results:
- Dexamethasone significantly increased survival rates in preterm pups exposed to hyperoxia.
- Preterm pups showed higher catalase and superoxide dismutase activities at birth after dexamethasone treatment.
- No significant differences in antioxidant enzyme activities were observed post-hyperoxia in preterm or term pups.
Conclusions:
- Prenatal dexamethasone enhances early survival and specific antioxidant enzyme levels at birth in preterm neonates.
- The protective effects of prenatal dexamethasone on antioxidant enzyme activity are not sustained after early postnatal hyperoxic exposure.
- Further research is needed to understand the long-term implications of prenatal steroid exposure on neonatal antioxidant defense mechanisms.
Abstract:
Although prenatal steroid therapy is known to enhance in utero maturation of the surfactant and antioxidant enzyme systems, little is known about the effects of steroids on the antioxidant system after birth. We measured activities of the antioxidant enzymes, catalase, superoxide dismutase, and glutathione peroxidase, in lung homogenates from both preterm and term rat pups after prenatal dexamethasone treatment. Enzyme activities were measured at birth and after exposure to > 98% oxygen. Dexamethasone treatment resulted in significantly higher survival of the preterm pups at 24 h (91.3% for dexamethasone versus 57% for saline). In preterm pups, the activities of catalase and superoxide dismutase at birth were higher after dexamethasone treatment (p < 0.05). However, after 24 h of hyperoxic exposure, there were no differences in activities of any of the antioxidant enzymes between the dexamethasone and control groups of prematurely born pups. In term pups, antioxidant enzyme activities did not differ significantly at birth; nor did they differ after 24 to 72 h of hyperoxic exposure in the dexamethasone and control treatment groups. Our results indicate that although prenatal dexamethasone treatment augments survival and catalase and superoxide dismutase activities at birth in preterm rat pups, dexamethasone does not result in altered early postnatal antioxidant enzyme activities after exposure to hyperoxia.