Ischemia increases prostaglandin H synthase-2 levels in retina and visual cortex in piglets.
BACKGROUND
Ischemia increases levels of prostaglandin H synthase-2 (PGHS-2) in neonatal brain and cerebral vasculature, but effects on the developing visual system are unknown. We examined the effects of ischemia on PGHS-2 mRNA and protein levels in the retina and visual cortex in anesthetized piglets.


METHODS
Ten minutes of complete retinal and brain ischemia was induced by increasing intracranial pressure. After 2-12 h of reperfusion, samples of retina and visual cortex were collected for determinations of levels of PGHS-2 mRNA (RNase protection assay) or protein (immunohistochemistry and western blotting). Tissues also were obtained from control animals.


RESULTS
Levels of PGHS-2 mRNA were undetectable in control animals but showed a dramatic increase at 2-4 h in the cortex and retina in animals exposed to ischemia. Detectable but limited PGHS-2 immunoreactivity (IR) was present in the retina and visual cortex from control animals. In piglets not subjected to ischemia, PGHS-2 IR was localized mainly to the outer limiting membrane and to the Muller cells. Ischemia induced a marked increase in PGHS-2 IR in the neural retina, with the greatest increase in the photoreceptor layer. PGHS-2 levels in whole retina also increased at 8 h after ischemia. In the intact visual cortex PGHS-2 IR was evident in layers II and V. Ischemia increased the intensity of IR in layers II/III as well as layer V.


CONCLUSIONS
Detectable amounts of PGHS-2 protein are present in the piglet retina and visual cortex under normal conditions, but levels are markedly increased 8-12 h after ischemic stress. Enhanced PGHS-2 levels after ischemic stress may contribute to delayed pathological changes of the visual system in the neonate.
Dégi
R
R
Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1083, USA.
Thore
C
C
Bari
F
F
Thrikawala
N
N
Nógrádi
A
A
Robins
G
G
Domoki
F
F
Beasley
T C
TC
Busija
D W
DW
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D051546:Cyclooxygenase 2; D005260:Female; D007124:Immunoenzyme Techniques; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008297:Male; D023282:Nuclease Protection Assays; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D015427:Reperfusion Injury / Q000201:enzymology* / Q000473:pathology; D012160:Retina / Q000201:enzymology* / Q000473:pathology; D013552:Swine; D015854:Up-Regulation; D014793:Visual Cortex / Q000201:enzymology* / Q000473:pathology
D007527:Isoenzymes; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases