Repeated prenatal corticosteroids reduce glial fibrillary acidic protein in the ovine central nervous system.
BACKGROUND
A single course of corticosteroid reduces intracranial hemorrhage in preterm infants. The mechanism of protection is unclear. Glial fibrillary acidic protein (GFAP), expressed by astrocytes, is regulated by glucosteroids and is an important component of the cells forming the blood brain barrier. We have evaluated the effect of prenatal corticosteroid upon ovine GFAP.


METHODS
Date-mated ewes were studied in two protocols and lambs delivered on day 125 or 145 (term = 150). In the maternal injection protocol (n = 36) ewes were administered saline, single or repeated injections of corticosteroid. In the fetal injection protocol (n = 48) direct ultrasound-guided fetal injections of saline, single or repeated corticosteroid were administered, and an additional control group did not receive fetal injections. Optic nerve GFAP immunohistochemistry was performed and quantified.


RESULTS
At 125 days, repeated, but not single, administration of corticosteroid, by either maternal or fetal route, was associated with a significant reduction in GFAP (both p < 0.002); by 145 days, the deficit had recovered (both p > 0.05). The process of performing repeated fetal injections had an independent effect upon GFAP at 145 days (p = 0.002).


CONCLUSIONS
Repeated administration of corticosteroid results in a reduction in GFAP in the developing ovine optic nerve, with recovery demonstrated by 145 days.
Quinlivan
Julie A
JA
Department of Obstetrics and Gynecology, Melbourne University, Victoria, Australia. julieq@unimelb.edu.au
Beazley
Lyn D
LD
Archer
Michael
M
Evans
Sharon F
SF
Newnham
John P
JP
Dunlop
Sarah A
SA
D000818:Animals; D001253:Astrocytes / Q000737:chemistry; D001623:Betamethasone / Q000008:administration & dosage / Q000009:adverse effects; D001724:Birth Weight / Q000187:drug effects; D005260:Female; D005865:Gestational Age; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis*; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000009:adverse effects*; D007150:Immunohistochemistry; D007267:Injections; D008431:Maternal-Fetal Exchange; D009900:Optic Nerve / Q000737:chemistry / Q000187:drug effects / Q000196:embryology*; D011247:Pregnancy; D012756:Sheep
D005904:Glial Fibrillary Acidic Protein; D005938:Glucocorticoids; D001623:Betamethasone